Personally, I don't think Wade and Christy are related. There are no in-game quotes that reflect it that I've ever heard, and Christy is a consistant victim of Wade and his friends.
I can see Gloria and Bo and Lance maybe being related. But, again, nothing to really indicate that they are (other than race). I tend to think Fatty and Karen are NOT related, nor are they related to Cornelius Johnson. Why so many same names in this game, by the way?
No way Bif and Zoe are related. Maybe Sheldon and Ted Thompson are brothers though? lol
I dunno, I have issues with how many same names are in this game. I realize that if you look through the yearbook of an average high school, you are gonna see numerous people with the same name. But there are what? 62 characters at the school in this game? They all should have distinctive names, with maybe one or two special cases. Nevermind that there is a Gord AND a Gordon.... and there is someone with Gurney as a last name AND a first name. I have NEVER heard the name Gurney anywhere.