While we don't live together, I think this story is relevant to the current conversation.
My boyfriend, T-Rex, spends Tuesday and Saturday nights with me while my husband, Thumper, is at work. Sunday mornings, when Thumper comes home, we fire up the airbed in the living room so we can have breakfast, watch movies, play video games, chat, listen to audio books, and have playful sex. These mornings often last until five or six at night. My daughter stays at my mom's on Sundays.
This past Sunday, over the course of such a 'morning', Thumper was sitting on the edge of the airbed looking up something on his laptop (which was set up on a TV tray next to the airbed) pertinent to a conversation he and T-Rex were having. Meanwhile, T-Rex and I had been casually fooling around under the covers.
So, T-Rex rolls over and is about to mount me (yay!) and Thumper starts talking about whatever it was he was looking up. He glances over, sees T-Rex poised for action, and says something like, "Oh, sorry. I'll wait."
T-Rex cheerfully says, "No no, go ahead, finish your thought," while continuing to... well, you know... initiate docking procedures.
Meanwhile, I start giggling. I have no clue what the topic was because my brain goes mushy at such times.
So Thumper says whatever he was going to say and T-Rex (who has achieved full penetration at this point) answers him thoughtfully. I think there may have been a brief conversational exchange at this point, but my memory is fuzzy there. Then T-Rex turns his full attention to me and we have a lovely bit of sex.
Mind you, T-Rex and I had plenty of intense one on one time the night before, so I didn't feel at all ignored or anything. I think I already had sex with Thumper that morning, probably with both of them, possibly at the same time, but Sunday mornings are lazy and fuzzy and warm, and we don't keep track or score or anything. They all kind of blur together in my memory.
Anyhow, T-Rex and I finish and take a moment for a cuddle. Thumper, who has been on the computer the whole time and was sitting on the airbed right next to us, laughs and says, "You know, it's really hard to use a mouse while you guys are doing that." He then pantomimes the effect all the bouncing had on his mousing skills.
I thought that was pretty funny, and T-Rex has a rich, booming laugh that is pleasant to feel resonating through his chest when I'm cuddled up against him.
It was awfully nice. I love the sense of camaraderie that has developed between them.
This makes me think that we possibly could all live together someday, though I'm not making any plans at this point. It's too soon and there's no real need for it. But at least the sex wouldn't be a problem.
I guess my point is that the sex doesn't have to be a problem, but it's something the metamours need to work out between them. I've been with T-Rex for about 8 months now, and this has developed slowly over time. We used to keep it separate and T-Rex would leave when Thumper came home (though that didn't last long), then we all started just hanging out together Sunday mornings, then it progressed to cuddling while hanging out, then light fondling under the covers entered the picture, and now it's this friendly and affectionate experience that is super warm and fuzzy.
It helps that we were all good friends before I became intimate with T-Rex.