It's not a secret that men's friendship has always been considered to be much stronger than women's one - some people even claim women can't make friends at all! We have no right to agree or disagree, but one thing is obvious - if there're two men friends and a woman appears, the chances of staying friends are gradually dicreasing... especially if the woman is one of the guy's sister! Sounds familiar? Wait a second, now it's going to look familiar, too!