that's too much for many too understandExactly. The only reason that Joey have them on the character sheet is because he wanted the family tree on there. They have no bearing on the story (no, not even the mythological sister ) other than to get some sympathy towards the MC and explain his history.
dead relation who are not die during the game = just info and background about character and with many character it's normal he do a tree even with the dead to keep in mind the background more easily just watching the tree when he do dialogue who talk about past stuff