Need help :)

I'm looking for a manga that I read a long time ago. The plot is about a girl in high school that has only one friend and its a guy. She has a little brother but does not like him because her mom had an affair and had him. The girl starts going out with a guy but does not know that he's her little brother's, brother..... Her mom had a car accident and died with her lover. Her little brother gets run over where his mom died. That's all I remember, plz help me find the name plz :D