Click on the link to read how to update the birth date associated with your Apple ID'- Update the birth date associated with your Apple ID - Apple Support
- "Be sure to enter your correct date of birth. After you change it to any age below 13, you can't edit it."
For a child with age set under 13 (or in a country where your offspring is considered to be a child) you will have to contact Apple:
Click here --> Choose your country or region - Official Apple Support Select your country, then a product and work your way down the menu until you reach the help you need. If you do not find it, select a different topic and work you way down to any option that results in a telephone or chat request.
Contact Apple for support and service - "See a list of Apple phone numbers around the world." - Contact Apple for support and service - Apple Support