Hypothetically speaking... If a guy was married, and he and his wife had a shared "girlfriend", and all three were exclusive to each other, like a "normal" relationship except for the fact that there is 3 people involved. Is this scenario even possible in the long term? given that everyone is emotionally mature and stable. And that there is no dishonesty amongst the 3 people. it wouldn't be just be purely a sexual relationship, (although there would be plenty of that ) but rather more of a love/emotional relationship among the 3. I suppose one of the first hurdle that comes to mind is eventuality of jealousy, and preference for one over the other. any thoughts?