What does he do? How does he change his mind?

Okay so one of my best friends has a girlfriend and I know he really loves her and theye been together for awhile, but his girlfriends broter absoluetly HATEs him. Not sure why though. He LOVEs his girlfriend. And she loves him. But her brother tells her she can't talk to him for whatever reason even though he knows that he is in love with her and treat her like an angel. And he knows that she loves him and thinks all of the decisions he makes are best for his little sister even though she knows that they aren't the best and he doesn't wanna mess with the brother cuz he's 280 lbs and can bench press 500 . And Se doesn't want him to mess with him cuz he is 17 and so he could really in a sense beat the crap out of him and get in little to no trouble whatsoever! And he doesn't want him to talk to her because he cussed but that is something he says he can fix! He doesn't even know him... So maye he should meet him before he listens to what everyone else says bout him ?! So basicly he just needs to know how to get him to change his mind about him. Oh , and he knows for a fact he is absoluetly in love with her!