I entered the wrong year on my childs birthdate, what do I need to do to fix the problem.
Posted on Nov 28, 2015 8:22 AM
Q: what do i need to do, if i entered the wrong birthdate for my childs account
"The birthday for a child's account can't be changed after the account is created. Be sure to enter the correct date."
From: Family Sharing and Apple ID for your child - Apple Support
You will have to create a new one.