How can I upgrade my son’s Xbox child account to an Adults?

Hi,CJ! I'm Luis, a fellow Xbox Gamer . Thanks for reaching us out here.

Unfortunately promoting a child account to an adult one is impossible. But you can cjange his privacy seetings.

Open the Xbox Family Settings app on your mobile device, and then go to Settings.

Select the Social tile to view or change how members can communicate with other players while they’re online.

Select the Cross-network play tile, and then select the communication level for the member in your family group.

As far as I know Child Accounts are not eligible to upgrade to a Family Pack sub. Maybe someone else can confirm this as truth or not?

If that is the case and your sons account is a Child Account then you'll need an Adult Account to make the purchase.

But the Family Pack FAQ should answer the most common questions going.

You will either have to download the game on an Xbox 360 or upgrade your account to an adult.

This is how you upgrade:
support.xbox.com/.../promote-child-account

A child account can be upgraded to adult by the parental account only when the child account reaches 18+

You can't change a child account into an adult account once registered for xbox live. You can modify the DOB under your MS account's page yet that will not upgrade a child account into an adult account for the live service.