Inviting Someone to My Apple Family account

I wanted to add someone to my Apple family account. We are both over 18; however, when I click 'Add', it takes me straight to creating a child account, with no other menu to add someone, and no way to exit that menu to add someone. I just click 'Add', and it takes me straight to creating an Apple child account. I click 'X', and it takes me back to the start menu. Please help :)