I know how you're feeling. When I found out my WAS was "sleeping with" someone -- meaning he wouldn't admit to an R but I'm not an idiot and I suspect he had a PA with her before we split, too --, it turns out I know her husband. An acquaintance only, but still. They're D-ing and things are pretty bitter on his (the husband's) end.
I was SO tempted to reach out to him but decided to keep to my own sandbox and see what plays out.
Instead, I'll settle for praying for their marriage and asking God to reconcile their commitment to each other.
ME: 38 BF: 40 T: 10y, no kids, no M (by choice) BD: 7/14/14, BF admits to PA, wants out, lies about new R. 10/1/14: I move out, BF lies about move in with OW 12/4/14: OW confronted, reveals all the lies