how old do u have to be to be able to set up family sharing

How old do you have to be to set up family sharing? I just joined apple music and choose the family plan to be able to let my brother join as well without having to pay and ive searched how to let him join my account and it says he can via family sharing. However, when i go to set it up, it says i need an adult Im curious as to the age i need to be to be able to set it up.