How to remove or change adult account on a childs account?

How to change child account to an adult account

I can't remember 100% but I am sure whoever set up the child account can change it. Like if you made an adult account on the xbox before making the child account that adult account can change wether the child account is a child account or and adult one.
I will just test this out myself now and post how it went

The first thing i tried was to change the child account into an adult account and to remove it from the fanily, but this doesnt work. Changing the birth date in child accounts is not possible, dont know why.

You can remove an account from a family group. The account will still exist, but it won't have the benefits or restrictions it had when it was within the family group. To remove a member from your family group, you must have an adult account, and be the
one who gave consent.

1. 1
   Go to family.microsoft.com.
   
2. 2
   Sign in with your Microsoft account, then:
   • To remove a child, scroll down and select Manage my child's profile info, select the child, select Remove consent for this child's account, and confirm. Then, go back to your family’s page, and under the child’s name, select More
     options > Remove from family, and confirm.
   • To remove a child because they’re now an adult, or if an adult account has been misclassified as a child account, verify the account.
   • To remove an adult, under that person's name, select More options > Remove from family, and confirm.
   • To leave the family group if you’re the only adult in the family, remove all children first, then find your name, select Leave family, and confirm. You must be over the statutory age to remove yourself.
   • If you're incorrectly listed as a child when you're an adult, see How to change a birthdate on a Microsoft account.

As said there is no way to change your child's account to an adult account until the age of birth you have put has reached the age of an Adult for your specific region. There are some troubleshooting tips that if your account is past the birthday and still
a child's account there is a way to promote to an adult account.

https://answers.microsoft.com/en-us/windows/forum/games_windows_10/how-to-change-child-account-to-ad...