Insert a htab group in another htabs group

Hello,

on my user edit form, i have several htab groups and htabs groups (image). I want to assemble the htab groups.
I have tried this hook in my template.php but without success :
My principal htabs group is "group_test" and my htab group is "['group_other_informations']".

$form['profile_custom']['#groups']['group_other_informations']['parent_name'] = 'group_test';

How should I proceed?

Thanks for your help.