This is from what I could gather in the games, since I know a lot of this isn’t going to be explained in the anime, sob. ;___;
Otoya: Mother died in a plane crash when he was little so he was raised in an orphanage. Doesn’t know who his father is (Shining lol)
Masato: Has both of his parents but his father is really strict and his mother is very sickly and she’s in the hospital most of the time. Also has a little sister, Mai (she’s…five, I think?)
Natsuki: Has both parents and is an only child (I believe) + Satsuki lololol
Tokiya: Is also an only child and his father walked out on him and his mother when he was small. His mother also has been pushing him to get into show business since he was little. (This is what I’m getting from his SS route, someone correct me or clarify if I’m wrong pleeease!)
Ren: Has two older brothers and both his parents have passed away
Syo: Mother is an orchestra conductor (mostly works overseas) and father is a stylist for the Shining Agency. Also has a younger twin brother, Kaoru, who is studying to be a doctor at Saotome Gakuen’s sister school.