Deleting child’s old apple accounts
How to delete a child’s old apple account if unable to login to that account?
iPhone 13, iOS 15
Question marked as
You can't delete the account if you can't sign in. See the Apple Support article(s) below.
How to delete your Apple ID account - Apple Support
Why can't you sign in?
If you forgot the Apple ID (iCloud) password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification email option if necessary. Link to contact Apple Support at the end of the 2nd article.