diff --git a/core/modules/block_content/block_content.install b/core/modules/block_content/block_content.install
index fab15b4f88..e8ee49260e 100644
--- a/core/modules/block_content/block_content.install
+++ b/core/modules/block_content/block_content.install
@@ -140,17 +140,27 @@ function block_content_update_8400() {
 }
 
 /**
- * Add 'reusable' field to 'block_content' entities.
+ * Add parent entity fields to 'block_content' entities.
  */
 function block_content_update_8600() {
-  $reusable = BaseFieldDefinition::create('boolean')
-    ->setLabel(t('Reusable'))
-    ->setDescription(t('A boolean indicating whether this block is reusable.'))
+  $update_manager = \Drupal::entityDefinitionUpdateManager();
+  $parent_entity_type = BaseFieldDefinition::create('string')
+    ->setLabel(t('Parent entity type'))
+    ->setDescription(t('The parent entity type.'))
     ->setTranslatable(FALSE)
     ->setRevisionable(FALSE)
-    ->setDefaultValue(TRUE)
-    ->setInitialValue(TRUE);
+    ->setDefaultValue('')
+    ->setInitialValue('');
 
-  \Drupal::entityDefinitionUpdateManager()
-    ->installFieldStorageDefinition('reusable', 'block_content', 'block_content', $reusable);
+  $update_manager->installFieldStorageDefinition('parent_entity_type', 'block_content', 'block_content', $parent_entity_type);
+
+  $parent_entity_id = BaseFieldDefinition::create('string')
+    ->setLabel(t('Parent ID'))
+    ->setDescription(t('The parent entity ID.'))
+    ->setTranslatable(FALSE)
+    ->setRevisionable(FALSE)
+    ->setDefaultValue('')
+    ->setInitialValue('');
+
+  $update_manager->installFieldStorageDefinition('parent_entity_id', 'block_content', 'block_content', $parent_entity_id);
 }
diff --git a/core/modules/block_content/block_content.module b/core/modules/block_content/block_content.module
index 71e1ee44d6..31435c176b 100644
--- a/core/modules/block_content/block_content.module
+++ b/core/modules/block_content/block_content.module
@@ -115,43 +115,43 @@ function block_content_add_body_field($block_type_id, $label = 'Body') {
  * Alters any 'entity_reference' query where the entity type is
  * 'block_content' and the query has the tag 'block_content_access'.
  *
- * These queries should only return reusable blocks unless a condition on
- * reusable is explicitly set.
+ * These queries should only return with no parent blocks unless a condition on
+ * parent is explicitly set.
  *
- * Since block_content entities can be set to be non-reusable they should by
+ * Since block_content entities can be set to be have a parent they should by
  * default not be selectable as entity reference values. A module can still
  * create a instance of
  * \Drupal\Core\Entity\EntityReferenceSelection\SelectionInterface
- * that will will allow selection of non-reusable blocks by explicitly setting
- * a condition on the reusable field.
+ * that will will allow selection of blocks with parents by explicitly setting
+ * a condition on either parent_entity_id or parent_entity_type fields.
  *
  * @see \Drupal\block_content\BlockContentAccessControlHandler
  */
 function block_content_query_entity_reference_alter(AlterableInterface $query) {
   if ($query instanceof SelectInterface && $query->getMetaData('entity_type') === 'block_content' && $query->hasTag('block_content_access')) {
     $data_table = \Drupal::entityTypeManager()->getDefinition('block_content')->getDataTable();
-    if (array_key_exists($data_table, $query->getTables()) && !_block_content_has_reusable_condition($query->conditions())) {
-      // If no reusable condition create a condition set to TRUE.
-      $query->condition("$data_table.reusable", TRUE);
+    if (array_key_exists($data_table, $query->getTables()) && !_block_content_has_parent_entity_condition($query->conditions())) {
+      // If no parent entity condition create a condition.
+      $query->isNull("$data_table.parent_entity_type");
     }
   }
 }
 
 /**
- * Utility function to find nested conditions using the reusable field.
+ * Utility function to find nested conditions using the parent entity fields.
  *
  * @param array $condition
  *   The condition or condition group to check.
  *
  * @return bool
- *   Whether the conditions contain any condition using the reusable field.
+ *   Whether conditions contain any condition using the parent entity fields.
  */
-function _block_content_has_reusable_condition(array $condition) {
+function _block_content_has_parent_entity_condition(array $condition) {
   // If this is a condition group call this function recursively for each nested
   // condition until a condition is found that return TRUE.
   if (isset($condition['#conjunction'])) {
     foreach (array_filter($condition, 'is_array') as $nested_condition) {
-      if (_block_content_has_reusable_condition($nested_condition)) {
+      if (_block_content_has_parent_entity_condition($nested_condition)) {
         return TRUE;
       }
     }
@@ -160,13 +160,15 @@ function _block_content_has_reusable_condition(array $condition) {
   if (isset($condition['field'])) {
     $field = $condition['field'];
     if (is_object($field) && $field instanceof ConditionInterface) {
-      return _block_content_has_reusable_condition($field->conditions());
+      return _block_content_has_parent_entity_condition($field->conditions());
     }
     $field_parts = explode('.', $field);
-    $data_table = $data_table = \Drupal::entityTypeManager()->getDefinition('block_content')->getDataTable();
+    $data_table = \Drupal::entityTypeManager()->getDefinition('block_content')->getDataTable();
     // With nested conditions the data table may have a suffix at the end like
     // 'block_content_field_data_2'.
-    return strpos($field_parts[0], $data_table) === 0 && $field_parts[1] === 'reusable';
+    if (strpos($field_parts[0], $data_table) === 0) {
+      return $field_parts[1] === 'parent_entity_id' || $field_parts[1] === 'parent_entity_type';
+    }
   }
   return FALSE;
 }
diff --git a/core/modules/block_content/block_content.post_update.php b/core/modules/block_content/block_content.post_update.php
index 927e588068..d71f5758b2 100644
--- a/core/modules/block_content/block_content.post_update.php
+++ b/core/modules/block_content/block_content.post_update.php
@@ -6,9 +6,9 @@
  */
 
 /**
- * Adds 'reusable filter to a Custom Block views.
+ * Adds 'has_parent' filter to Custom Block views.
  */
-function block_content_post_update_add_views_reusable_filter() {
+function block_content_post_update_add_views_parent_filter() {
   $config_factory = \Drupal::configFactory();
   $data_table = \Drupal::entityTypeManager()
     ->getDefinition('block_content')
@@ -21,17 +21,17 @@ function block_content_post_update_add_views_reusable_filter() {
     }
     foreach ($view->get('display') as $display_name => $display) {
       // Update the default display and displays that have overridden filters.
-      if (!isset($display['display_options']['filters']['reusable']) &&
+      if (!isset($display['display_options']['filters']['has_parent']) &&
         ($display_name === 'default' || isset($display['display_options']['filters']))) {
         // Save off the base part of the config path we are updating.
-        $base = "display.$display_name.display_options.filters.reusable";
-        $view->set("$base.id", 'reusable')
-          ->set("$base.plugin_id", 'boolean')
+        $base = "display.$display_name.display_options.filters.has_parent";
+        $view->set("$base.id", 'has_parent')
+          ->set("$base.plugin_id", 'boolean_string')
           ->set("$base.table", $data_table)
-          ->set("$base.field", "reusable")
-          ->set("$base.value", "1")
+          ->set("$base.field", "has_parent")
+          ->set("$base.value", '0')
           ->set("$base.entity_type", "block_content")
-          ->set("$base.entity_field", "reusable");
+          ->set("$base.entity_field", "parent_entity_type");
       }
     }
     $view->save();
diff --git a/core/modules/block_content/config/optional/views.view.block_content.yml b/core/modules/block_content/config/optional/views.view.block_content.yml
index 2c008864f3..b4de8c1859 100644
--- a/core/modules/block_content/config/optional/views.view.block_content.yml
+++ b/core/modules/block_content/config/optional/views.view.block_content.yml
@@ -431,15 +431,15 @@ display:
           entity_type: block_content
           entity_field: type
           plugin_id: bundle
-        reusable:
-          id: reusable
+        has_parent:
+          id: has_parent
           table: block_content_field_data
-          field: reusable
+          field: has_parent
           relationship: none
           group_type: group
           admin_label: ''
           operator: '='
-          value: '1'
+          value: '0'
           group: 1
           exposed: false
           expose:
@@ -467,8 +467,8 @@ display:
             default_group_multiple: {  }
             group_items: {  }
           entity_type: block_content
-          entity_field: reusable
-          plugin_id: boolean
+          entity_field: parent_entity_type
+          plugin_id: boolean_string
       sorts: {  }
       title: 'Custom block library'
       header: {  }
diff --git a/core/modules/block_content/src/BlockContentAccessControlHandler.php b/core/modules/block_content/src/BlockContentAccessControlHandler.php
index 2ad950f4d0..34077b82af 100644
--- a/core/modules/block_content/src/BlockContentAccessControlHandler.php
+++ b/core/modules/block_content/src/BlockContentAccessControlHandler.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\block_content;
 
-use Drupal\Core\Access\AccessDependentInterface;
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityAccessControlHandler;
@@ -27,15 +26,14 @@ protected function checkAccess(EntityInterface $entity, $operation, AccountInter
       $access = parent::checkAccess($entity, $operation, $account);
     }
     /** @var \Drupal\block_content\BlockContentInterface $entity */
-    if ($entity->isReusable() === FALSE) {
-      if (!$entity instanceof AccessDependentInterface) {
-        throw new \LogicException("Non-reusable block entities must implement \Drupal\Core\Access\AccessDependentInterface for access control.");
+    if ($entity->hasParentEntity()) {
+      if ($parent_entity = $entity->getParentEntity()) {
+        $access = $access->andIf($parent_entity->access($operation, $account, TRUE))->addCacheableDependency($entity);
       }
-      $dependency = $entity->getAccessDependency();
-      if (empty($dependency)) {
-        return AccessResult::forbidden("Non-reusable blocks must set an access dependency for access control.");
+      else {
+        // The entity has a parent but it was not able to be loaded.
+        return AccessResult::forbidden('Parent entity not available.')->addCacheableDependency($entity);
       }
-      $access->andIf($dependency->access($operation, $account, TRUE))->addCacheableDependency($access);
     }
     return $access;
   }
diff --git a/core/modules/block_content/src/BlockContentInterface.php b/core/modules/block_content/src/BlockContentInterface.php
index 50fabdfb1a..16d427561e 100644
--- a/core/modules/block_content/src/BlockContentInterface.php
+++ b/core/modules/block_content/src/BlockContentInterface.php
@@ -2,16 +2,16 @@
 
 namespace Drupal\block_content;
 
-use Drupal\Core\Access\AccessDependentInterface;
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Entity\EntityChangedInterface;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityPublishedInterface;
 use Drupal\Core\Entity\RevisionLogInterface;
 
 /**
  * Provides an interface defining a custom block entity.
  */
-interface BlockContentInterface extends ContentEntityInterface, EntityChangedInterface, RevisionLogInterface, EntityPublishedInterface, AccessDependentInterface {
+interface BlockContentInterface extends ContentEntityInterface, EntityChangedInterface, RevisionLogInterface, EntityPublishedInterface {
 
   /**
    * Returns the block revision log message.
@@ -49,24 +49,6 @@ public function setInfo($info);
    */
   public function setRevisionLog($revision_log);
 
-  /**
-   * Determines if the block is reusable or not.
-   *
-   * @return bool
-   *   Returns TRUE if reusable and FALSE otherwise.
-   */
-  public function isReusable();
-
-  /**
-   * Sets the block to be reusable.
-   *
-   * @param bool $reusable
-   *   Whether the block should be reusable, defaults to TRUE.
-   *
-   * @return $this
-   */
-  public function setReusable($reusable = TRUE);
-
   /**
    * Sets the theme value.
    *
@@ -102,4 +84,41 @@ public function getTheme();
    */
   public function getInstances();
 
+  /**
+   * Sets the parent entity.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $parent_entity
+   *   The parent entity.
+   *
+   * @return \Drupal\block_content\BlockContentInterface
+   *   The class instance that this method is called on.
+   */
+  public function setParentEntity(EntityInterface $parent_entity);
+
+  /**
+   * Gets the parent entity.
+   *
+   * @return \Drupal\Core\Entity\EntityInterface|null
+   *   The parent entity or null if none exists.
+   *
+   * @todo How to deterine parent is set but no longer exists.
+   */
+  public function getParentEntity();
+
+  /**
+   * Removes the parent entity.
+   *
+   * @return \Drupal\block_content\BlockContentInterface
+   *   The class instance that this method is called on.
+   */
+  public function removeParentEntity();
+
+  /**
+   * Whether the block has a parent entity set.
+   *
+   * @return bool
+   *   TRUE if a parent entity is set, otherwise FALSE.
+   */
+  public function hasParentEntity();
+
 }
diff --git a/core/modules/block_content/src/BlockContentListBuilder.php b/core/modules/block_content/src/BlockContentListBuilder.php
index 88545e09b4..8467c3c3e0 100644
--- a/core/modules/block_content/src/BlockContentListBuilder.php
+++ b/core/modules/block_content/src/BlockContentListBuilder.php
@@ -33,9 +33,8 @@ public function buildRow(EntityInterface $entity) {
    */
   protected function getEntityIds() {
     $query = $this->getStorage()->getQuery()
-      ->sort($this->entityType->getKey('id'));
-
-    $query->condition('reusable', TRUE);
+      ->sort($this->entityType->getKey('id'))
+      ->notExists('parent_entity_type');
 
     // Only add the pager if a limit is specified.
     if ($this->limit) {
diff --git a/core/modules/block_content/src/BlockContentViewsData.php b/core/modules/block_content/src/BlockContentViewsData.php
index e9ff0eb4cd..de3df7af6a 100644
--- a/core/modules/block_content/src/BlockContentViewsData.php
+++ b/core/modules/block_content/src/BlockContentViewsData.php
@@ -21,6 +21,18 @@ public function getViewsData() {
     $data['block_content_field_data']['info']['field']['id'] = 'field';
     $data['block_content_field_data']['info']['field']['link_to_entity default'] = TRUE;
 
+    $data['block_content_field_data']['has_parent'] = [
+      'title' => $this->t('Has Parent'),
+      'help' => $this->t('Whether the block has a parent'),
+      'field' => ['id' => 'field'],
+      'filter' => [
+        'id' => 'boolean_string',
+        'accept_null' => TRUE,
+      ],
+      'entity field' => 'parent_entity_type',
+      'real field' => 'parent_entity_type',
+    ];
+
     $data['block_content_field_data']['type']['field']['id'] = 'field';
 
     $data['block_content_field_data']['table']['wizard_id'] = 'block_content';
diff --git a/core/modules/block_content/src/Entity/BlockContent.php b/core/modules/block_content/src/Entity/BlockContent.php
index 2995e99cec..ba5002f634 100644
--- a/core/modules/block_content/src/Entity/BlockContent.php
+++ b/core/modules/block_content/src/Entity/BlockContent.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\block_content\Entity;
 
-use Drupal\Core\Access\AccessDependentTrait;
 use Drupal\Core\Entity\EditorialContentEntityBase;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Field\BaseFieldDefinition;
@@ -78,8 +78,6 @@
  */
 class BlockContent extends EditorialContentEntityBase implements BlockContentInterface {
 
-  use AccessDependentTrait;
-
   /**
    * The theme the block is being created in.
    *
@@ -121,7 +119,7 @@ public function getTheme() {
    */
   public function postSave(EntityStorageInterface $storage, $update = TRUE) {
     parent::postSave($storage, $update);
-    if ($this->isReusable() || (isset($this->original) && $this->original->isReusable())) {
+    if (empty($this->get('parent_entity_type')->value) || (isset($this->original) && empty($this->original->get('parent_entity_type')->value))) {
       static::invalidateBlockPluginCache();
     }
   }
@@ -133,8 +131,8 @@ public static function postDelete(EntityStorageInterface $storage, array $entiti
     parent::postDelete($storage, $entities);
     /** @var \Drupal\block_content\BlockContentInterface $block */
     foreach ($entities as $block) {
-      if ($block->isReusable()) {
-        // If any deleted blocks are reusable clear the block cache.
+      if (!$block->hasParentEntity()) {
+        // If any deleted blocks do not have a parent ID clear the block cache.
         static::invalidateBlockPluginCache();
         return;
       }
@@ -212,13 +210,23 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setTranslatable(TRUE)
       ->setRevisionable(TRUE);
 
-    $fields['reusable'] = BaseFieldDefinition::create('boolean')
-      ->setLabel(t('Reusable'))
-      ->setDescription(t('A boolean indicating whether this block is reusable.'))
+    // @todo Is there a core issue to add
+    //   https://www.drupal.org/project/dynamic_entity_reference
+    $fields['parent_entity_type'] = BaseFieldDefinition::create('string')
+      ->setLabel(t('Parent entity type'))
+      ->setDescription(t('The parent entity type.'))
+      ->setTranslatable(FALSE)
+      ->setRevisionable(FALSE)
+      ->setDefaultValue(NULL)
+      ->setInitialValue(NULL);
+
+    $fields['parent_entity_id'] = BaseFieldDefinition::create('string')
+      ->setLabel(t('Parent ID'))
+      ->setDescription(t('The parent entity ID.'))
       ->setTranslatable(FALSE)
       ->setRevisionable(FALSE)
-      ->setDefaultValue(TRUE)
-      ->setInitialValue(TRUE);
+      ->setDefaultValue(NULL)
+      ->setInitialValue(NULL);
 
     return $fields;
   }
@@ -302,26 +310,48 @@ public function setRevisionLogMessage($revision_log_message) {
     return $this;
   }
 
+  /**
+   * Invalidates the block plugin cache after changes and deletions.
+   */
+  protected static function invalidateBlockPluginCache() {
+    // Invalidate the block cache to update custom block-based derivatives.
+    \Drupal::service('plugin.manager.block')->clearCachedDefinitions();
+  }
+
   /**
    * {@inheritdoc}
    */
-  public function isReusable() {
-    return (bool) $this->get('reusable')->value;
+  public function setParentEntity(EntityInterface $parent_entity) {
+    $this->set('parent_entity_type', $parent_entity->getEntityTypeId());
+    $this->set('parent_entity_id', $parent_entity->id());
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function setReusable($reusable = TRUE) {
-    return $this->set('reusable', $reusable);
+  public function getParentEntity() {
+    if ($this->hasParentEntity()) {
+      return \Drupal::entityTypeManager()->getStorage($this->get('parent_entity_type')->value)->load($this->get('parent_entity_id')->value);
+    }
+    return NULL;
   }
 
   /**
-   * Invalidates the block plugin cache after changes and deletions.
+   * {@inheritdoc}
    */
-  protected static function invalidateBlockPluginCache() {
-    // Invalidate the block cache to update custom block-based derivatives.
-    \Drupal::service('plugin.manager.block')->clearCachedDefinitions();
+  public function removeParentEntity() {
+    $this->set('parent_entity_type', NULL);
+    $this->set('parent_entity_id', NULL);
+    return $this;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function hasParentEntity() {
+    // If either parent field value is set then the block is considered to have
+    // a parent.
+    return !empty($this->get('parent_entity_type')->value) || !empty($this->get('parent_entity_id')->value);
+  }
 }
diff --git a/core/modules/block_content/src/Plugin/Derivative/BlockContent.php b/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
index ba1ab98968..edf82bc46a 100644
--- a/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
+++ b/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
@@ -43,10 +43,11 @@ public static function create(ContainerInterface $container, $base_plugin_id) {
    * {@inheritdoc}
    */
   public function getDerivativeDefinitions($base_plugin_definition) {
-    $block_contents = $this->blockContentStorage->loadByProperties(['reusable' => TRUE]);
+    $block_ids = $this->blockContentStorage->getQuery()->notExists('parent_entity_type')->execute();
+    $block_contents = $this->blockContentStorage->loadMultiple($block_ids);
     // Reset the discovered definitions.
     $this->derivatives = [];
-    /** @var $block_content \Drupal\block_content\Entity\BlockContent */
+    /* @var $block_content \Drupal\block_content\Entity\BlockContent */
     foreach ($block_contents as $block_content) {
       $this->derivatives[$block_content->uuid()] = $base_plugin_definition;
       $this->derivatives[$block_content->uuid()]['admin_label'] = $block_content->label();
diff --git a/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php b/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php
index 6072501537..6c4bfcf336 100644
--- a/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php
+++ b/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php
@@ -20,14 +20,15 @@ class BlockContent extends WizardPluginBase {
    */
   public function getFilters() {
     $filters = parent::getFilters();
-    $filters['reusable'] = [
-      'id' => 'reusable',
-      'plugin_id' => 'boolean',
+    $filters['has_parent'] = [
+      'id' => 'has_parent',
+      'plugin_id' => 'boolean_string',
       'table' => $this->base_table,
-      'field' => 'reusable',
-      'value' => '1',
+      'field' => 'has_parent',
+      'operator' => '=',
+      'value' => '0',
       'entity_type' => $this->entityTypeId,
-      'entity_field' => 'reusable',
+      'entity_field' => 'parent_entity_type',
     ];
     return $filters;
   }
diff --git a/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php b/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php
index 82b8aa90dc..1c3f753478 100644
--- a/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php
+++ b/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php
@@ -5,7 +5,7 @@
 use Drupal\Core\Entity\Plugin\EntityReferenceSelection\DefaultSelection;
 
 /**
- * Test EntityReferenceSelection class that adds various 'reusable' conditions.
+ * Test EntityReferenceSelection that adds various parent entity conditions.
  */
 class TestSelection extends DefaultSelection {
 
@@ -31,33 +31,35 @@ public function setTestMode($testMode) {
    */
   protected function buildEntityQuery($match = NULL, $match_operator = 'CONTAINS') {
     $query = parent::buildEntityQuery($match, $match_operator);
+    if (strpos($this->testMode, 'parent_entity_id') === 0) {
+      $field = 'parent_entity_id';
+    }
+    else {
+      $field = 'parent_entity_type';
+    }
     switch ($this->testMode) {
-      case 'reusable_condition_false':
-        $query->condition("reusable", 0);
-        break;
-
-      case 'reusable_condition_exists':
-        $query->exists('reusable');
+      case "{$field}_condition_false":
+        $query->notExists($field);
         break;
 
-      case 'reusable_condition_group_false':
+      case "{$field}_condition_group_false":
         $group = $query->andConditionGroup()
-          ->condition("reusable", 0)
+          ->notExists($field)
           ->exists('type');
         $query->condition($group);
         break;
 
-      case 'reusable_condition_group_true':
+      case "{$field}_condition_group_true":
         $group = $query->andConditionGroup()
-          ->condition("reusable", 1)
+          ->exists($field)
           ->exists('type');
         $query->condition($group);
         break;
 
-      case 'reusable_condition_nested_group_false':
+      case "{$field}_condition_nested_group_false":
         $query->exists('type');
         $sub_group = $query->andConditionGroup()
-          ->condition("reusable", 0)
+          ->notExists($field)
           ->exists('type');
         $group = $query->andConditionGroup()
           ->exists('type')
@@ -65,10 +67,10 @@ protected function buildEntityQuery($match = NULL, $match_operator = 'CONTAINS')
         $query->condition($group);
         break;
 
-      case 'reusable_condition_nested_group_true':
+      case "{$field}_condition_nested_group_true":
         $query->exists('type');
         $sub_group = $query->andConditionGroup()
-          ->condition("reusable", 1)
+          ->exists($field)
           ->exists('type');
         $group = $query->andConditionGroup()
           ->exists('type')
diff --git a/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml b/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml
index a3cc406077..1c95f9f854 100644
--- a/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml
+++ b/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml
@@ -4,8 +4,6 @@ dependencies:
   module:
     - block_content
     - user
-_core:
-  default_config_hash: gkRJCqHr3uSO8ALHLatX-7YKfX0lWEgkC5qMBtCf_Sg
 id: block_content
 label: 'Custom block library'
 module: views
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
index 8919c05d00..12a8dcc129 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
@@ -108,17 +108,17 @@ public function testListing() {
     $this->assertText(t('There are no custom blocks yet.'));
 
     $block_content = BlockContent::create([
-      'info' => 'Non-reusable block',
+      'info' => 'Block with parent',
       'type' => 'basic',
-      'reusable' => FALSE,
     ]);
+    $block_content->setParentEntity($this->loggedInUser);
     $block_content->save();
 
     $this->drupalGet('admin/structure/block/block-content');
     // Confirm that the empty text is displayed.
     $this->assertSession()->pageTextContains('There are no custom blocks yet.');
-    // Confirm the non-reusable block is not on the page.
-    $this->assertSession()->pageTextNotContains('Non-reusable block');
+    // Confirm the block with a parent is not on the page.
+    $this->assertSession()->pageTextNotContains('Block with parent');
   }
 
 }
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
index f9cf29eb77..8a229e742c 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
@@ -116,17 +116,17 @@ public function testListing() {
     $this->assertLink('custom block');
 
     $block_content = BlockContent::create([
-      'info' => 'Non-reusable block',
+      'info' => 'Block with parent',
       'type' => 'basic',
-      'reusable' => FALSE,
     ]);
+    $block_content->setParentEntity($this->loggedInUser);
     $block_content->save();
 
     $this->drupalGet('admin/structure/block/block-content');
     // Confirm that the empty text is displayed.
     $this->assertSession()->pageTextContains('There are no custom blocks available.');
-    // Confirm the non-reusable block is not on the page.
-    $this->assertSession()->pageTextNotContains('Non-reusable block');
+    // Confirm the Block with parent is not on the page.
+    $this->assertSession()->pageTextNotContains('Block with parent');
   }
 
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
index 4a3ac11f4c..13b2df05b1 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
@@ -92,11 +92,8 @@ protected function getExpectedNormalizedEntity() {
           'value' => 'en',
         ],
       ],
-      'reusable' => [
-        [
-          'value' => TRUE,
-        ],
-      ],
+      'parent_entity_type' => [],
+      'parent_entity_id' => [],
       'type' => [
         [
           'target_id' => 'basic',
diff --git a/core/modules/block_content/tests/src/Functional/Update/BlockContentParentEntityUpdateTest.php b/core/modules/block_content/tests/src/Functional/Update/BlockContentParentEntityUpdateTest.php
new file mode 100644
index 0000000000..bd7cf0d771
--- /dev/null
+++ b/core/modules/block_content/tests/src/Functional/Update/BlockContentParentEntityUpdateTest.php
@@ -0,0 +1,168 @@
+<?php
+
+namespace Drupal\Tests\block_content\Functional\Update;
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+use Drupal\views\Entity\View;
+
+/**
+ * Tests entity parent fields update functions for the Block Content module.
+ *
+ * @group Update
+ */
+class BlockContentParentEntityUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
+    ];
+  }
+
+  /**
+   * Tests adding parent entity fields to the block content entity type.
+   *
+   * @see block_content_update_8600
+   * @see block_content_post_update_add_views_parent_filter
+   */
+  public function testParentFieldsAddition() {
+    $assert_session = $this->assertSession();
+    $entity_definition_update_manager = \Drupal::entityDefinitionUpdateManager();
+
+    // Delete custom block library view.
+    View::load('block_content')->delete();
+    // Install the test module with the 'block_content' view with an extra
+    // display with overridden filters. This extra display should also have the
+    // 'has_parent' filter added so that it does not expose fields with parents
+    // This display also a filter  only show blocks that contain 'block2' in the
+    // 'info' field.
+    $this->container->get('module_installer')->install(['block_content_view_override']);
+
+    // Run updates.
+    $this->runUpdates();
+
+    // Check that the 'parent_entity_type' field exists and is configured
+    // correctly.
+    $parent_type_field = $entity_definition_update_manager->getFieldStorageDefinition('parent_entity_type', 'block_content');
+    $this->assertEquals('Parent entity type', $parent_type_field->getLabel());
+    $this->assertEquals('The parent entity type.', $parent_type_field->getDescription());
+    $this->assertEquals(FALSE, $parent_type_field->isRevisionable());
+    $this->assertEquals(FALSE, $parent_type_field->isTranslatable());
+
+    // Check that the 'parent_entity_id' field exists and is configured
+    // correctly.
+    $parent_id_field = $entity_definition_update_manager->getFieldStorageDefinition('parent_entity_id', 'block_content');
+    $this->assertEquals('Parent ID', $parent_id_field->getLabel());
+    $this->assertEquals('The parent entity ID.', $parent_id_field->getDescription());
+    $this->assertEquals(FALSE, $parent_id_field->isRevisionable());
+    $this->assertEquals(FALSE, $parent_id_field->isTranslatable());
+
+    $after_block1 = BlockContent::create([
+      'info' => 'After update block1',
+      'type' => 'basic_block',
+    ]);
+    $after_block1->save();
+    // Add second block that will be shown with the 'info' filter on the
+    // additional view display.
+    $after_block2 = BlockContent::create([
+      'info' => 'After update block2',
+      'type' => 'basic_block',
+    ]);
+    $after_block2->save();
+
+    $this->assertEquals(FALSE, $after_block1->hasParentEntity());
+    $this->assertEquals(FALSE, $after_block2->hasParentEntity());
+
+    $admin_user = $this->drupalCreateUser(['administer blocks']);
+    $this->drupalLogin($admin_user);
+
+    $block_with_parent = BlockContent::create([
+      'info' => 'block1 with parent',
+      'type' => 'basic_block',
+    ]);
+    $block_with_parent->setParentEntity($admin_user);
+    $block_with_parent->save();
+    // Add second block that would be shown with the 'info' filter on the
+    // additional view display if the 'has_parent' filter was not added.
+    $block2_with_parent = BlockContent::create([
+      'info' => 'block2 with parent',
+      'type' => 'basic_block',
+    ]);
+    $block2_with_parent->setParentEntity($admin_user);
+    $block2_with_parent->save();
+    $this->assertEquals(TRUE, $block_with_parent->hasParentEntity());
+    $this->assertEquals(TRUE, $block2_with_parent->hasParentEntity());
+
+
+
+    // Ensure the Custom Block view shows the blocks without parents only.
+    $this->drupalGet('admin/structure/block/block-content');
+    file_put_contents('/Users/ted.bowman/Sites/www/test.html', $this->getSession()->getPage()->getOuterHtml());
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseContains('view-id-block_content');
+    $assert_session->pageTextContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_with_parent->label());
+    $assert_session->pageTextNotContains($block2_with_parent->label());
+
+    // Ensure the view's other display also only shows blocks without parent and
+    // still filters on the 'info' field.
+    $this->drupalGet('extra-view-display');
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseContains('view-id-block_content');
+    $assert_session->pageTextNotContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_with_parent->label());
+    $assert_session->pageTextNotContains($block2_with_parent->label());
+
+    // Ensure the Custom Block listing without Views installed shows the only
+    // blocks without parents.
+    $this->drupalGet('admin/structure/block/block-content');
+    $this->container->get('module_installer')->uninstall(['views_ui', 'views']);
+    $this->drupalGet('admin/structure/block/block-content');
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseNotContains('view-id-block_content');
+    $assert_session->pageTextContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_with_parent->label());
+    $assert_session->pageTextNotContains($block2_with_parent->label());
+
+    $this->drupalGet('block/' . $after_block1->id());
+    $assert_session->statusCodeEquals('200');
+
+    // Ensure the user who can access a block parent they can access edit form
+    // edit route is not accessible.
+    $this->drupalGet('block/' . $block_with_parent->id());
+    $assert_session->statusCodeEquals('200');
+
+    $this->drupalLogout();
+
+    $this->drupalLogin($this->createUser([
+      'access user profiles',
+      'administer blocks',
+    ]));
+    $this->drupalGet('block/' . $after_block1->id());
+    $assert_session->statusCodeEquals('200');
+
+    $this->drupalGet('block/' . $block_with_parent->id());
+    $assert_session->statusCodeEquals('403');
+
+    $this->drupalLogin($this->createUser([
+      'administer blocks',
+    ]));
+
+    $this->drupalGet('block/' . $after_block1->id());
+    $assert_session->statusCodeEquals('200');
+
+    $this->drupalGet('user/' . $admin_user->id());
+    $assert_session->statusCodeEquals('403');
+
+    $this->drupalGet('block/' . $block_with_parent->id());
+    $assert_session->statusCodeEquals('403');
+
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php b/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php
deleted file mode 100644
index 7803f40813..0000000000
--- a/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php
+++ /dev/null
@@ -1,131 +0,0 @@
-<?php
-
-namespace Drupal\Tests\block_content\Functional\Update;
-
-use Drupal\block_content\Entity\BlockContent;
-use Drupal\FunctionalTests\Update\UpdatePathTestBase;
-use Drupal\views\Entity\View;
-
-/**
- * Tests 'reusable' field related update functions for the Block Content module.
- *
- * @group Update
- */
-class BlockContentReusableUpdateTest extends UpdatePathTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setDatabaseDumpFiles() {
-    $this->databaseDumpFiles = [
-      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
-    ];
-  }
-
-  /**
-   * Tests adding a reusable field to the block content entity type.
-   *
-   * @see block_content_update_8600
-   * @see block_content_post_update_add_views_reusable_filter
-   */
-  public function testReusableFieldAddition() {
-    $assert_session = $this->assertSession();
-    $entity_definition_update_manager = \Drupal::entityDefinitionUpdateManager();
-
-    // Delete custom block library view.
-    View::load('block_content')->delete();
-    // Install the test module with the 'block_content' view with an extra
-    // display with overridden filters. This extra display should also have a
-    // filter added for 'reusable' field so that it does not expose non-reusable
-    // fields. This display also a filter  only show blocks that contain
-    // 'block2' in the 'info' field.
-    $this->container->get('module_installer')->install(['block_content_view_override']);
-
-    // Run updates.
-    $this->runUpdates();
-
-    // Check that the field exists and is configured correctly.
-    $reusable_field = $entity_definition_update_manager->getFieldStorageDefinition('reusable', 'block_content');
-    $this->assertEquals('Reusable', $reusable_field->getLabel());
-    $this->assertEquals('A boolean indicating whether this block is reusable.', $reusable_field->getDescription());
-    $this->assertEquals(FALSE, $reusable_field->isRevisionable());
-    $this->assertEquals(FALSE, $reusable_field->isTranslatable());
-
-    $after_block1 = BlockContent::create([
-      'info' => 'After update block1',
-      'type' => 'basic_block',
-    ]);
-    $after_block1->save();
-    // Add second block that will be shown with the 'info' filter on the
-    // additional view display.
-    $after_block2 = BlockContent::create([
-      'info' => 'After update block2',
-      'type' => 'basic_block',
-    ]);
-    $after_block2->save();
-
-    $this->assertEquals(TRUE, $after_block1->isReusable());
-    $this->assertEquals(TRUE, $after_block2->isReusable());
-
-    $non_reusable_block = BlockContent::create([
-      'info' => 'non-reusable block1',
-      'type' => 'basic_block',
-      'reusable' => FALSE,
-    ]);
-    $non_reusable_block->save();
-    // Add second block that will be would shown with the 'info' filter on the
-    // additional view display if the 'reusable filter was not added.
-    $non_reusable_block2 = BlockContent::create([
-      'info' => 'non-reusable block2',
-      'type' => 'basic_block',
-      'reusable' => FALSE,
-    ]);
-    $non_reusable_block2->save();
-    $this->assertEquals(FALSE, $non_reusable_block->isReusable());
-    $this->assertEquals(FALSE, $non_reusable_block2->isReusable());
-
-    $admin_user = $this->drupalCreateUser(['administer blocks']);
-    $this->drupalLogin($admin_user);
-
-    // Ensure the Custom Block view shows the reusable blocks but not
-    // the non-reusable block.
-    $this->drupalGet('admin/structure/block/block-content');
-    $assert_session->statusCodeEquals('200');
-    $assert_session->responseContains('view-id-block_content');
-    $assert_session->pageTextContains($after_block1->label());
-    $assert_session->pageTextContains($after_block2->label());
-    $assert_session->pageTextNotContains($non_reusable_block->label());
-    $assert_session->pageTextNotContains($non_reusable_block2->label());
-
-    // Ensure the views other display also filters out non-reusable blocks and
-    // still filters on the 'info' field.
-    $this->drupalGet('extra-view-display');
-    $assert_session->statusCodeEquals('200');
-    $assert_session->responseContains('view-id-block_content');
-    $assert_session->pageTextNotContains($after_block1->label());
-    $assert_session->pageTextContains($after_block2->label());
-    $assert_session->pageTextNotContains($non_reusable_block->label());
-    $assert_session->pageTextNotContains($non_reusable_block2->label());
-
-    $this->drupalGet('block/' . $after_block1->id());
-    $assert_session->statusCodeEquals('200');
-
-    // Ensure that non-reusable blocks edit form edit route is not accessible.
-    $this->drupalGet('block/' . $non_reusable_block->id());
-    $assert_session->statusCodeEquals('403');
-
-    // Ensure the Custom Block listing without Views installed shows the
-    // reusable blocks but not the non-reusable blocks.
-    // the non-reusable block.
-    $this->drupalGet('admin/structure/block/block-content');
-    $this->container->get('module_installer')->uninstall(['views_ui', 'views']);
-    $this->drupalGet('admin/structure/block/block-content');
-    $assert_session->statusCodeEquals('200');
-    $assert_session->responseNotContains('view-id-block_content');
-    $assert_session->pageTextContains($after_block1->label());
-    $assert_session->pageTextContains($after_block2->label());
-    $assert_session->pageTextNotContains($non_reusable_block->label());
-    $assert_session->pageTextNotContains($non_reusable_block2->label());
-  }
-
-}
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
index 2c59e5c50f..e765dd6684 100644
--- a/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
@@ -43,10 +43,10 @@ public function testViewAddBlockContent() {
 
     $display_options = $view->getDisplay('default')['display_options'];
 
-    $this->assertEquals('block_content', $display_options['filters']['reusable']['entity_type']);
-    $this->assertEquals('reusable', $display_options['filters']['reusable']['entity_field']);
-    $this->assertEquals('boolean', $display_options['filters']['reusable']['plugin_id']);
-    $this->assertEquals('1', $display_options['filters']['reusable']['value']);
+    $this->assertEquals('block_content', $display_options['filters']['has_parent']['entity_type']);
+    $this->assertEquals('parent_entity_type', $display_options['filters']['has_parent']['entity_field']);
+    $this->assertEquals('boolean_string', $display_options['filters']['has_parent']['plugin_id']);
+    $this->assertEquals('0', $display_options['filters']['has_parent']['value']);
   }
 
 }
diff --git a/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php b/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php
index 600fc75fab..dededb611a 100644
--- a/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php
+++ b/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php
@@ -6,6 +6,7 @@
 use Drupal\block_content\Entity\BlockContentType;
 use Drupal\Component\Plugin\PluginBase;
 use Drupal\KernelTests\KernelTestBase;
+use Drupal\user\Entity\User;
 
 /**
  * Tests block content plugin deriver.
@@ -25,14 +26,15 @@ class BlockContentDeriverTest extends KernelTestBase {
   public function setUp() {
     parent::setUp();
     $this->installSchema('system', ['sequence']);
+    $this->installSchema('system', ['sequences']);
     $this->installEntitySchema('user');
     $this->installEntitySchema('block_content');
   }
 
   /**
-   * Tests that only reusable blocks are derived.
+   * Tests that block with parents are not derived.
    */
-  public function testReusableBlocksOnlyAreDerived() {
+  public function testBlocksWithParentsNotDerived() {
     // Create a block content type.
     $block_content_type = BlockContentType::create([
       'id' => 'spiffy',
@@ -47,18 +49,23 @@ public function testReusableBlocksOnlyAreDerived() {
     ]);
     $block_content->save();
 
-    // Ensure the reusable block content is provided as a derivative block
+    // Ensure block entity with no parent is provided as a derivative block
     // plugin.
     /** @var \Drupal\Core\Block\BlockManagerInterface $block_manager */
     $block_manager = $this->container->get('plugin.manager.block');
     $plugin_id = 'block_content' . PluginBase::DERIVATIVE_SEPARATOR . $block_content->uuid();
     $this->assertTrue($block_manager->hasDefinition($plugin_id));
 
-    // Set the block not to be reusable.
-    $block_content->setReusable(FALSE);
+    // Set the block not to have a parent.
+    $user = User::create([
+      'name' => 'username',
+      'status' => 1,
+    ]);
+    $user->save();
+    $block_content->setParentEntity($user);
     $block_content->save();
 
-    // Ensure the non-reusable block content is not provided a derivative block
+    // Ensure the block content with a parent is not provided a derivative block
     // plugin.
     $this->assertFalse($block_manager->hasDefinition($plugin_id));
   }
diff --git a/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php b/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php
index 882e653eaf..d401c56ebc 100644
--- a/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php
+++ b/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php
@@ -6,9 +6,10 @@
 use Drupal\block_content\Entity\BlockContentType;
 use Drupal\block_content_test\Plugin\EntityReferenceSelection\TestSelection;
 use Drupal\KernelTests\KernelTestBase;
+use Drupal\user\Entity\User;
 
 /**
- * Tests EntityReference selection handlers don't return non-reusable blocks.
+ * Tests EntityReference selection handlers don't return blocks with parents.
  *
  * @see block_content_query_block_content_access_alter()
  *
@@ -40,6 +41,7 @@ class BlockContentEntityReferenceSelectionTest extends KernelTestBase {
   public function setUp() {
     parent::setUp();
     $this->installSchema('system', ['sequence']);
+    $this->installSchema('system', ['sequences']);
     $this->installEntitySchema('user');
     $this->installEntitySchema('block_content');
 
@@ -54,26 +56,31 @@ public function setUp() {
   }
 
   /**
-   * Tests that non-reusable blocks are not referenceable entities.
+   * Tests that blocks with parent are not referenceable entities.
    *
    * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
    * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
    * @throws \Exception
    */
   public function testReferenceableEntities() {
-    // And reusable and non-reusable block content entities.
-    $block_content_reusable = BlockContent::create([
-      'info' => 'Reusable Block',
+    $user = User::create([
+      'name' => 'username',
+      'status' => 1,
+    ]);
+    $user->save();
+
+    // And block content entities with and without parents.
+    $block_content = BlockContent::create([
+      'info' => 'Block no parent',
       'type' => 'spiffy',
-      'reusable' => TRUE,
     ]);
-    $block_content_reusable->save();
-    $block_content_nonreusable = BlockContent::create([
-      'info' => 'Non-reusable Block',
+    $block_content->save();
+    $block_content_with_parent = BlockContent::create([
+      'info' => 'Block with parent',
       'type' => 'spiffy',
-      'reusable' => FALSE,
     ]);
-    $block_content_nonreusable->save();
+    $block_content_with_parent->setParentEntity($user);
+    $block_content_with_parent->save();
 
     // Ensure that queries without all the tags are not altered.
     $query = $this->entityTypeManager->getStorage('block_content')->getQuery();
@@ -89,7 +96,7 @@ public function testReferenceableEntities() {
 
     // Use \Drupal\Core\Entity\Plugin\EntityReferenceSelection\DefaultSelection
     // class to test that getReferenceableEntities() does not get the
-    // non-reusable entity.
+    // entity wth a parent.
     $configuration = [
       'target_type' => 'block_content',
       'target_bundles' => ['spiffy' => 'spiffy'],
@@ -99,61 +106,57 @@ public function testReferenceableEntities() {
     // Setup the 3 expectation cases.
     $both_blocks = [
       'spiffy' => [
-        $block_content_reusable->id() => $block_content_reusable->label(),
-        $block_content_nonreusable->id() => $block_content_nonreusable->label(),
+        $block_content->id() => $block_content->label(),
+        $block_content_with_parent->id() => $block_content_with_parent->label(),
       ],
     ];
-    $reusable_block = ['spiffy' => [$block_content_reusable->id() => $block_content_reusable->label()]];
-    $non_reusable_block = ['spiffy' => [$block_content_nonreusable->id() => $block_content_nonreusable->label()]];
+    $block_no_parent = ['spiffy' => [$block_content->id() => $block_content->label()]];
+    $block_with_parent = ['spiffy' => [$block_content_with_parent->id() => $block_content_with_parent->label()]];
 
     $this->assertEquals(
-      $reusable_block,
+      $block_no_parent,
       $selection_handler->getReferenceableEntities()
     );
 
     // Test various ways in which an EntityReferenceSelection plugin could set
-    // the 'reusable' condition. If the plugin has set a condition on 'reusable'
-    // at all then 'block_content_query_entity_reference_alter()' will not set
-    // a reusable condition.
-    $selection_handler->setTestMode('reusable_condition_false');
-    $this->assertEquals(
-      $non_reusable_block,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    $selection_handler->setTestMode('reusable_condition_exists');
-    $this->assertEquals(
-      $both_blocks,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    $selection_handler->setTestMode('reusable_condition_group_false');
-    $this->assertEquals(
-      $non_reusable_block,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    $selection_handler->setTestMode('reusable_condition_group_true');
-    $this->assertEquals(
-      $reusable_block,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    $selection_handler->setTestMode('reusable_condition_nested_group_false');
-    $this->assertEquals(
-      $non_reusable_block,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    $selection_handler->setTestMode('reusable_condition_nested_group_true');
-    $this->assertEquals(
-      $reusable_block,
-      $selection_handler->getReferenceableEntities()
-    );
-
-    // Change the block to reusable.
-    $block_content_nonreusable->setReusable(TRUE);
-    $block_content_nonreusable->save();
+    // a condition on either the 'parent_entity_id' or 'parent_entity_type'
+    // fields. If the plugin has set a condition on either of these fields
+    // then 'block_content_query_entity_reference_alter()' will not set
+    // a parent condition.
+    foreach (['parent_entity_id', 'parent_entity_type'] as $field) {
+      $selection_handler->setTestMode("{$field}_condition_false");
+      $this->assertEquals(
+        $block_no_parent,
+        $selection_handler->getReferenceableEntities()
+      );
+
+      $selection_handler->setTestMode("{$field}_condition_group_false");
+      $this->assertEquals(
+        $block_no_parent,
+        $selection_handler->getReferenceableEntities()
+      );
+
+      $selection_handler->setTestMode("{$field}_condition_group_true");
+      $this->assertEquals(
+        $block_with_parent,
+        $selection_handler->getReferenceableEntities()
+      );
+
+      $selection_handler->setTestMode("{$field}_condition_nested_group_false");
+      $this->assertEquals(
+        $block_no_parent,
+        $selection_handler->getReferenceableEntities()
+      );
+
+      $selection_handler->setTestMode("{$field}_condition_nested_group_true");
+      $this->assertEquals(
+        $block_with_parent,
+        $selection_handler->getReferenceableEntities()
+      );
+    }
+
+    $block_content_with_parent->removeParentEntity();
+    $block_content_with_parent->save();
     // Don't use any conditions.
     $selection_handler->setTestMode(NULL);
     // Ensure that the block is now returned as a referenceable entity.