Yes, my wife found out that a guy that I'd vetted for one of her gangbangs was married and was cheating on his wife. At the time it didn't bother us, and even made her more turned on in some ways. The guy himself was super excited and very enamored with my girl; later confessing that he didn't get any sex from his wife anymore; and even that was tame. So a girl like mine was like a goldmine for him to get out his sexual frustrations. She enjoyed his eagerness/aggressiveness so much that I "loaned" her to him for 24 hours one weekend. Dropped her off at a hotel one morning to meet him in the parking lot and picked her up the next morning. He turned her inside out all day and night in that time, it was spectacular.
We later made it a rule to let potential play partners know that while we prefer not to involve ourselves with cheaters, we acknowledge that people are people and to just leave us out of it. Works out best for everyone.