Let them be First of all, I do agree that incest isn't really bad. (I'm not saying this because of experiences) when siblings DO have sexual activities and they make a baby, then there's a percentage that the baby will have some genetically disordered disease. Then that is bad. BUT, who are you to judge them? If they love each other not as a brother and sister, but as a man and a woman, then let them be. They cause no harm to you guys. They love each other, you can't tell them NOT to love each other because loving is something that a person feels naturally. If incest is illegal, then why does some countries approve homosexual marriages? Is it because they're so many of them? Is it because there's an exceptional number of them? Is it because of bandwagon? Is it because they touched your hearts deep that you guys support them? Well, think about that for a second and then tell me, Is incest wrong? Why don't you do the same thing that you did when you approved with homosexual marriage? Why don't you support siblings who love each other because they just simply love each other?