I just found out some odd information about my friend. So him and his older brothers have a different father; his mother was married to his brothers' father. While his mother was separated from his brothers' father she had him. When he was born he was given his mother's married name, her estranged husband's last name . The husband knew he's not his son but still got back with the wife, but rejected my friend.
My friend knows who his real father is and has no relationship with him and of course no relationship to his "stepfather". How odd is it to have the last name of a man who isn't your father and doesn't like you, plus your actual father doesn't claim you either.
I don't know why his mother didn't just give him her maiden name.