I don't know that I would bring her family into it. I know if I were screwing up, bringing my family into it would just make me hate myself more and I would kill the messenger.
I think she's having horrible guilt issues.
I would, as the next step, make it obvious you are a better man then this jerk, bc you are. The good news is this will blow up.
I'm not opposed though to you calling this dude and simply saying--I don't know what you and my wife are talking about. I do know she and I are having some problems and I would appreciate it if you could back off just a bit and keep it professional only. If my marriage is going to fail, do you really want to be a part of that? I would rather know, she and I alone couldn't make it work--I don't want to wonder what if this other person didn't exist? Could we have made it then?"
Appeal to him being respectful of your marriage, your wife and you.
You do have a lot of questions and very few answers at this point.
