This self-proclaimed intellect called Cylegend never cease to amuse us. Ok here is the deal....let your sister stay with a guy without marrying him. Let her come back after couple of years with some kids and see how the culture and society reacts. It would be interesting to see your face too. My friend, even dogs and donkeys make babies and continue their species. We are supposed to be homo sapiens and are obliged under certain rules which has been the norm of civilized societies. No matter what, do not ever forget the ground where you stand.