You could be a little more creative, you could do some sport game, any game actually and the only way of winning is teamwork, this is a small example, but this is how i learned to work with my brother. In this situation a small game can change something, beside that, this situation need a lot of talking, not only about the problems, you should talk about some nice and hard subjects like the future. Each son could say something, doctor, policeman, if they have similar ideas you can use that, we need people with similarities by our side, friends, with team work similarities and some talking anything is possible.