I dated a guy briefly who was like this. I think he screwed every friends girlfriend. He went to all sorts of lengths to do it. I was always amazed at each new low. He definitely had mommy and daddy issues, feelings of not being accepted (he was born an outside child). I tried to have an intimate relationship with the guy, but every time it ended because of his insatiable appetite for someone else’s girlfriend and his lack of respect. Before one relationship or sex escapade was over, another was started. It left a trail of hurt friends and hurt women (girlfriends specifically).
He had kids with 5 different women, and has never been married. It just seems he enjoyed digging himself in a hole. I ended my friendship, because he refuses to get help or treat me the way I want to be treated. These types of people are dangerous because they violate norms and betray trust without remorse. The insecurity they leave behind is not worth it.