Facebook doesn't properly identify me vs my brother, so they still have some things to work one.
I think part of this is that their facial recognition doesn't have a logic check based on the other context data that they have.
eg. my brother's wife will post vacation photos of him, him with his kids, and him with her, and yet sometimes it still auto-identifies the pictures of him as me. Facebook knows I'm logged in at an ip 1000 miles away. Facebook knows my brother is with his wife because they both have logged in recently while on vacation. Yet I am tagged instead of him.