Hey there irfadino,
Thanks for reaching out to the community.
Work through the steps below to help get the child account moved to another family group:
Invite the child to another family
To move a child to another family group, you or another guardian needs to invite them. After you send the invitation, the child's current family organizer must approve the request on their iPhone, iPad, iPod touch, or Mac. Then the child will move from their current family group to the other family group.
Invite a child from your iPhone, iPad, or iPod touch
Learn how to invite the child in-person using the steps below.
In iOS 16 or later
1. Go to Settings.
2. Tap Family.
3. Tap the Add Member button.
4. Tap Invite Others.
5. Tap Invite in Person.
6. Ask the child to enter their Apple ID and password. Learn what to do if the child forgot their password.
7. Follow the onscreen steps.
8. After the child's current family organizer approves the request, follow the onscreen steps to provide parental consent and verify that you're an adult.
To check the status of the request, go to Settings, tap Family, then tap the child's name.
For help with an earlier iOS on or a Mac: Move a child to another group using Family Sharing - Apple Support
Take care!