How to add a date select inside a list

In Webform 2, I managed to create a list of radiobuttons with date components for each option. I did this by creating a 'radios'-element for each option, grouping them with the attribute #parents.
Example code:

$form['option_one'] = array(
    '#type' => 'radios',
    '#options' => array('0' => t("Exact date:")),
    '#weight' => 22,
    '#parents' => array('mygroup'),
);

$form['option_one_date'] = array(
    '#type' => 'date_select',
    '#attributes' => array('class'=>'marginleft-20'),
    '#date_format' => 'd-F-Y',
    '#date_year_range' => '0:+5',
    '#date_label_position' => 'none',
    '#weight' => 23,
);

$form['option_two'] = array(
    '#type' => 'radios',
    '#options' => array('1' => t("Approximately:")),
    '#weight' => 24,
    '#parents' => array('mygroup'),
);

$form['option_two_date'] = array(
    '#type' => 'date_select',
    '#attributes' => array('class'=>'marginleft-20'),
    '#date_format' => 'd-F-Y',
    '#date_year_range' => '0:+5',
    '#date_label_position' => 'none',
    '#weight' => 25,
);

$form['option_three'] = array(
    '#type' => 'radios',
    '#options' => array('2' => t("I'm not sure")),
    '#weight' => 26,
    '#parents' => array('mygroup'),
);

Look at the attachment to see the result of this code.

In Webform 3.2, it seems like the possibility to group items through #parents is not possible anymore.
How can I achieve this in Webform 3.2?