Can i change my child account to an adult account to add a custom profile picture?

Changing the birthdate under your profile doesn't changes your child account to adult.

Only the parental account can upgrade a child account when the service registers that the account has reached 18+

Unluckily only adult accounts can post custom profile pictures for obvious reasons

Your own custom picture in profile is only for adult account. You are child, your parents made for you child account.

Hey there Jacob!

Nice to meet you! My name is Christian, an independent advisor. I'm here to help you out.

I just want to clarify, are you trying to change your profile picture to a custom profile picture?

If you are trying to change your child account to an adult account, it will not be possible because even if you change your account's birthdate, the system will still detect that your account is a child account based on your account's birthdate upon creation.

The only way for a child account to graduate to an adult account is to wait until your original birthdate turns to 21 years old.

Hi, I hope you're doing great out there. I am an Independent advisor and I am here to help you in regard to your concern.

I'm sorry but no, Aidyn. Your account needs to naturally mature, this is when you're already an adult, your account will do too and you can then use a custom Gamerpic.

As for the custom profile picture, that is only available, if according to the birthdate entered when the account was created, the account reached legal adult age (and before you ask, no, changing the birthdate won't make the account an adult account. Currently
there is no way to change the birthdate of a Xbox account).

However, all other settings like allowing the kid to play age rated games for adults, talking to internet strangers etc. can be set through your adult account.

Go to
https://account.microsoft.com/family, sign in with your own adult account and add your child's account to your adult parent account if not already done so.

If you have your child's account added to your adult parent account, you can go to
https://account.xbox.com/settings and sign in with your adult account again.

There you can then click on your child's account and make the necessary changes to the account's online and privacy settings, so it can be as unrestricted as an adult account, in regards to the online and privacy settings (which doesn't include custom gamerpics
yet).