The brain doesn't stop growing until around age 25. When a brain is still growing it causes impulse control issues. Obviously, your son has a problem controlling his urges. You would think after one child; he would learn and take his relationships seriously, nope. While you cannot enable his behavior, you can still influence him, and that starts by spending time with him. Men do not form attachments to their children in the same way women do. A man needs to be a daily part of his child's life to feel that attachment. Right now your son is being selfish because he doesn't know the consequences of not being a good father. He doesn't know he could mess up this little girl for life. But you can show him that the world is full of broken little girls who do all manner of self-deprecating activities because their fathers were not around. If he is not willing to step up for this child, then maybe you should consider being there for her. As for your son, it sounds like he is very irresponsible. I usually tell parents to get the kid to work for you. However, you seem to know him pretty well, what is he predisposed to do? Mechanic? Truck driver? What is he good at? Push him that way. It's tough to find your niche when you are young. Point him in the right direction, and if you let him move back in, charge him rent.