Mark is your older brother, but you left the rich life as soon as you could because you hated that your parents flaunted you around rather than loving you like a daughter. You gave up the fortune and cut contact with everyone who had anything to do with your old life so you haven't spoken to Mark in years.

Mark is now a successful plastic surgeon at Grey Sloan memorial hospital in Seatle and you moved there recently too.

Neither of you knew about the other living in Seatle until you got into a car accident and he ended up stumbling across the OR you're in.