I’m not a FB subscriber, but wonder if it’s typical for an adult to open an account for a underage kid?
Anyone can open an account ... underage or not ... and even though Facebook requires the proper age and requires that your information be real and correct ... you can still open an account with no problem.
HOWEVER ... anyone can report any violation on your account ... so it pays to have everything “right” on your account so no one can report you for any technical violations.
You have to be a “real person” with the correct name and details given on your account ... or else you are in violation and your account can be deleted or blocked.