Boyfriends brother disslikes me. Today when i was gonna hug him goodbye he gave me a really big fake smile... :/ i try to get to know him, give tips etc but he don't seem to like me. How will this effect my relationship?

Me (almost 22f) and bf (24m) have talked about getting kids, house etc the next 5 upcoming years. So what should i do to get along with his brother?