There is this guy he is like a brother but he told my best friend That he likes me he has had a girl friend ?

he has had his girl friend for about 11 months and me and her a friends but she went to a nother school and she has a nother boyfriend now but her and my friend that likes me still go out but he wants to go out with me and to add on top of that his girl friend cousin is like one of my best friend and gos to school with us and his tein sister and me are like real sisters i dont kno if she will take that the right way what do you think? should i go out with him