I need to know if this is wrong.?

Well, theres this really really really REALLY.hot guy and he flirts with me. Like on the trampoline everytime i sit down he eather grabs my hands and pulls me up and jumps with me or lays with me, also he hugs ne holds my hand and calls me pretty. He always stands next to me and everything and i flirt back but we just found out that hes my moms boyfriends brothers sun... there not married but is it wrong that we're doing this? Were not dating.