I think it is very wrong that the Husband has confided in you something he has not told the wife yet and is expecting you to keep his secret for him. He's splitting your loyalty between him and his wife. Yuck. He's placed you in a very awkward position. How is his wife going to feel when she knows you knew about this other woman when she didn't? He is not being a good friend. I would tell him I don't want to be his confidante anymore.

I would support both of them in efforts to go to counseling. They need it. The marriage therapist can help them, even if they end up splitting up. My former husband and I went to couples therapy for quite some time after we decided to split up and it was very helpful. Just because you decide to divorce doesn't help with the pain, and a therapist can help with that. I think the therapist, if he/she is any good, will quickly realize the H does not want to stay in the marriage and will get to the heart of the issue and help the H tell the wife what he needs to, and maybe in a way that can promote some healing. The therapist can also be a support for the wife when she realizes this is the end of the relationship (if this is what happens).