diff --git a/core/modules/taxonomy/src/Entity/Term.php b/core/modules/taxonomy/src/Entity/Term.php
index 8cbfdda..a4435dd 100644
--- a/core/modules/taxonomy/src/Entity/Term.php
+++ b/core/modules/taxonomy/src/Entity/Term.php
@@ -73,12 +73,14 @@ public static function postDelete(EntityStorageInterface $storage, array $entiti
     /** @var \Drupal\taxonomy\TermInterface $term */
     foreach ($entities as $tid => $term) {
       if ($children = $term->getChildren()) {
+        /** @var \Drupal\taxonomy\TermInterface $child */
         foreach ($children as $child) {
+          $parent = $child->get('parent');
           // Update child parents item list.
-          $child->getParents()->removeItemsByTargetId($tid);
+          $parent->removeItemsByTargetId($tid);
 
           // If the term has multiple parents, we don't delete it.
-          if ($child->getParents()->count()) {
+          if ($parent->count()) {
             $child->save();
           }
           else {
@@ -99,7 +101,7 @@ public static function postDelete(EntityStorageInterface $storage, array $entiti
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
     // Terms with no parents are mandatory children of <root>.
-    if (!$this->getParents()->count()) {
+    if (!$this->get('parent')->count()) {
       $this->parent->target_id = 0;
     }
   }
@@ -244,7 +246,18 @@ public function getVocabularyId() {
    * {@inheritdoc}
    */
   public function getParents() {
-    return $this->get('parent');
+    $parents = $ids = [];
+    // Cannot use $this->get('parent')->referencedEntities() here because that
+    // strips out the '0' reference.
+    foreach ($this->get('parent') as $item) {
+      if ($item->target_id == 0) {
+        // The <root> parent.
+        $parents[0] = NULL;
+        continue;
+      }
+      $ids[] = $item->target_id;
+    }
+    return $parents + static::loadMultiple($ids);
   }
 
   /**
@@ -256,10 +269,10 @@ public function getAncestors() {
       $search[] = $this->id();
 
       while ($tid = array_shift($search)) {
-        foreach (static::load($tid)->getParents() as $parent) {
-          if (!empty($parent->entity) && !isset($this->ancestors[$parent->target_id])) {
-            $this->ancestors[$parent->target_id] = $parent->entity;
-            $search[] = $parent->target_id;
+        foreach (static::load($tid)->getParents() as $id => $parent) {
+          if (!empty($parent) && !isset($this->ancestors[$id])) {
+            $this->ancestors[$id] = $parent;
+            $search[] = $id;
           }
         }
       }
@@ -270,12 +283,9 @@ public function getAncestors() {
   /**
    * {@inheritdoc}
    */
-  public function getChildren($vid = NULL) {
+  public function getChildren() {
     $query = \Drupal::entityQuery('taxonomy_term')
       ->condition('parent', $this->id());
-    if ($vid) {
-      $query->condition('vid', $vid);
-    }
     return static::loadMultiple($query->execute());
   }
 
diff --git a/core/modules/taxonomy/src/TermHierarchyInterface.php b/core/modules/taxonomy/src/TermHierarchyInterface.php
index 98f3054..b4de45a 100644
--- a/core/modules/taxonomy/src/TermHierarchyInterface.php
+++ b/core/modules/taxonomy/src/TermHierarchyInterface.php
@@ -12,9 +12,9 @@
   /**
    * Returns a list of parents of this term.
    *
-   * @return \Drupal\Core\Field\EntityReferenceFieldItemListInterface
-   *   A list of references to parents taxonomy terms. If this term has a <root>
-   *   parent that item is keyed with 0 and have NULL as value.
+   * @return \Drupal\taxonomy\TermInterface[]
+   *   The parent taxonomy term entities keyed by term id. If this term has a
+   *   <root> parent, that item is keyed with 0 and will have NULL as value.
    */
   public function getParents();
 
@@ -29,12 +29,9 @@ public function getAncestors();
   /**
    * Returns all children terms of this term.
    *
-   * @param string $vid
-   *   An optional vocabulary ID to restrict the child search.
-   *
    * @return \Drupal\taxonomy\TermInterface[]
    *   A list of children taxonomy term entities keyed by term id.
    */
-  public function getChildren($vid = NULL);
+  public function getChildren();
 
 }
diff --git a/core/modules/taxonomy/src/TermStorage.php b/core/modules/taxonomy/src/TermStorage.php
index 34bf462..326b76a 100644
--- a/core/modules/taxonomy/src/TermStorage.php
+++ b/core/modules/taxonomy/src/TermStorage.php
@@ -83,11 +83,11 @@ public function loadParents($tid) {
     $terms = [];
     /** @var \Drupal\taxonomy\TermInterface $term */
     if ($tid && $term = $this->load($tid)) {
-      foreach ($term->getParents() as $delta => $item) {
+      foreach ($term->getParents() as $id => $parent) {
         // This method currently doesn't return the <root> parent.
         // @see https://www.drupal.org/node/2019905
-        if (!empty($item->entity)) {
-          $terms[$item->target_id] = $item->entity;
+        if (!empty($id)) {
+          $terms[$id] = $parent;
         }
       }
     }
@@ -108,7 +108,7 @@ public function loadAllParents($tid) {
    */
   public function loadChildren($tid, $vid = NULL) {
     /** @var \Drupal\taxonomy\TermInterface $term */
-    return (!empty($tid) && $term = $this->load($tid)) ? $term->getChildren($vid) : [];
+    return (!empty($tid) && $term = $this->load($tid)) ? $term->getChildren() : [];
   }
 
   /**