13 under changing age

On your iPhone, iPad, or iPod touch

1. Go to Settings > [your name].
2. Tap Name, Phone Numbers, Email. You might need to enter your Apple ID password.
3. Tap Change Birthday or Birthday.
4. Update your birth date, then tap Done. If you're changing a birth date for a child, learn what to do.

Update the birth date associated with your Apple ID

Nope, you cannot edit the age if it is 13 or under. You will see this statement in that link:

• After you change a birth date to any age below 13, you can't edit it.