I have been close friends with a married man for almost two years and we’ve never slept together. I really care about him though, and him about me. Is it ever ok to have a sexual relationship with a man who is married to someone else?
Sure. Just get the thumbs up from his wife, and you’re all good to fuck.
Infidelity isn’t about the sex. It’s about the breach of integrity. If his wife doesn’t mind sharing, and all three of you are open and honest about your intentions and desires, then whatever sex you have won’t be a breach of integrity.
Short of that, don’t do it. Trust me. Married people are a package deal, and it’s always better to be open with a couple than to have an affair with just the one, because either way, you’ll end up fucking them both.