Feel bad for her? Yes. Make it about me? No. I have known people who have cheated who I would trust with my life. It is so vain to assume someone who cheated on someone else revolves around YOU. I have never cheated on anyone. But that is just such a strange logic to me. If you felt weird about it, just say you do not want to be around him if he is being sneaky. But your awkward vibe around his wife--especially if you were his friend long before you met her--makes me wonder if you have feelings for his wife as more than a friend. If you do, then this makes more sense to me. I would suggest having a talk with your friend though. You sound like you are walking into “he does not deserve you" territory and potentially becoming her shoulder to lean on, which is just as sneaky.