Microsoft Account says that it's in a family account

Hi, I hope you're doing great out there despite the issue that you're experiencing. I am an Independent advisor and I am here to help you in regards to your concern.

For you to manage it you can simply sign in to https://account.xbox.com/settings.

If the system detects that your account is a child account you will be redirected to a support site and if not you will be able to change it successfully.

If you were redirected to a support page, please sign in to https://account.microsoft.com/family and check if there is an organizer account linked to your account then use the organizer account so sign in to https://account.xbox.com/settings then "allow" the setting on this screenshot:

I would say check your Family account page
(details here.) See if there are other accounts you don't recognize in your account family? Or do you know if your account is listed as an alias on another MS Account?

No, my account is not a child's on a family account. It says that I am an adult on my family's account, not a child.

So are you part of a Family Plan? When you say points are you meaning Microsoft Points or Gamerscore? You cannot merge points or accounts or gamerscore. However if you are on the Family plan then you can Grant Allowance of Microsoft Points, if you know or
are the primary account holder.

The best method would be to have him use a child account, and use parental controls with a password locked family account. For more information, you can go here:

https://support.xbox.com/en-US/my-account/microsoft-account/microsoft-account-family-benefits