Of all the women or men in the world, why date your friend's X? A person that knowingly does this is truly disgusting! This very act happens daily in society, which lets you know how low-down this world has become.
When you're looking for a mate, pay attention to the signs. If a man doesn't respect or love his mother, how in the hell could he ever love or respect a wife? If a woman doesn't respect or love her father, why should she treat her husband any different?