With her sister’s ass it is impossible to avoid incest
He always thinks he shouldn’t do it. Especially with the stories his grandmother tells about the things the Bible says about it. Although he does not know that there was no other possible way for two people that God created to overpopulate the planet. Then they realize that with the ass their sister has, it is impossible to avoid incest. And he doesn’t, because when she gets into his bed naked to give him a cock suck, he doesn’t resist and lets her do it. Then he can pleasure himself with her pussy while he is penetrating her. He enjoys it and that’s what counts.