Pretty sure that's called "hot-wifing", but your probably going to tell us in great detail how hotwife and voluntary cuckold relationships are just one degree in the spectrum of ENM, instead of a wife who wants to enjoy extra dick while her husband waits at home or watches. Most people I've known who do this were socially-inept late bloomers and didn't have any or very little sexual experience before meeting and starting a relationship with their main partner who may have been their first sexual partner. Then one of them (usually the woman) starts thinking about what they missed out on by not having multiple playmates and the main guy (also usually socially inept and inexperienced and not wanting to lose this woman) talk and agree to open it up. The guy doesn't find anyone usually because he's happy with what he's got. The woman gets on some dating apps and meets some guys who want to fuck her (because she's got a pussy). She spends more time with one new guy and brings up the idea of polyamory to the old guy. New guy ends up moving in and they live as a throuple. Woman spends more time with new guy because he's new, and old guy either deals with it or gets upset. Most of these relationships don't last long - less than 5 years - because one person will eventually feel neglected. The ones that do are when the woman wants the 3rd to be another woman (bi tendencies) and the main woman sleeps with both but the man and new woman don't. Neither feel as threatened of being replaced by the other partner. There was a story I read a while back of a husband and wife in an ENM relationship with another guy who lived with them. She already had a kid with the husband. She wanted to get pregnant by the new guy and didn't want the baby born out of wedlock so she divorced her husband and married the new guy before the baby was born. They all three still lived together with now 2 kids. Seems fucked up for the kids, especially the one who now has divorced parents. What happens if she gets pregnant by the 1st guy again? And yes, almost every gay couple I know - including my best friend's relationship - are often going to parties or clubs or vacations or cruises and hooking up with whomever they can find. Every time I hear one of those stories or see pictures he took I just shake my head.