Damn, well it looks like your bro is trapped. Either he does his best to get over it and forget it, or he divorces his wife and potentially gets smacked by the family court legal system.. But even worse-his sons/future kids shot at a normal healthy family life is gone.

As much as I understand its simply in womens' nature to act this way, it still pisses me off when they do. Her husband was working his ass off to provide for his family. It's not like he was ditching his wife to go play video games and get drunk with his friends. And even then, he deserves one of those days now and then just as much as she deserves a night wine tasting with her girlfriends or some shit.

If I were him I'd do my best to forget about it and move on for the sake of my children. I'd also be hitting the gym hard and working to improve my looks and enforce dread game/hot and cold her. When the kids are all adults, just go for the divorce. I might even spin a couple plates in the meantime behind her back.

If you have abundance, you don't really GAF if a chick cheats on you. You just dump them and move on. But in a married with children situation, you have a kingdom to look over. I might also contact the guy she cheated with and tell him for the sake of his family to please stay away from his wife. I know it comes off beta, but some guys have a heart and can realize/learn what's right and wrong and back off.