1.) Step-bro #2. More of a jock type. Maybe his dad is more into the carrot than the stick, so instead of a bribe he gets threatened with something like getting pulled off of the basketball team?
2.) A meathead? Teammate and best friend of the above. A little too loud, not too bright, but a loyal friend.
3.) A tagalong. Maybe a little brother - not sure of who, either my jock or one of your two others - who is quiet and sensitive. The type to bring four books in his backpack to a weekend at the cabin.