He is your half-brother on your father's side, because your father had been with another woman, and that woman had had Robbie...he is 16, just like you, Peter, your real brother, he is 18 years old, he is two years older that you and Robbie... Robbie knows his mom and his dad, who is also yours. Peter doesn't like Robbie because he was the son of the woman dad had cheated on mom with. His birthday is the 24th. April, impressively the same day as you...they are both British with a thick accent