This is the one where Alice is the lesbian gf who has sex with the husband because the gf/wife wants that.
Ah, thanks, ref.
It seems to me that a queen or double bed with a single pushed up against it would work, or even just a king. Personally I dislike sharing a bed with 2 adult people on a regular basis. I did it once for a long weekend with my 2 partners at a kink con hotel stay. I was the hinge. We shared a king, and it felt roomy enough. But I was in the middle, so if I needed to get out of bed in the night to pee, I had to awkwardly climb down the middle of the bed to get out.
It's best to have separate sets of sheets and blankets or duvets, so you don't uncover anyone when getting out, or fight for the covers all night.
I could see getting too hot, or feeling cramped, especially if one was sick, or injured, had a bad back, etc. And what if someone worked late and came in, disturbing the other 2? I could see someone giving up on 3 in a bed, getting fed up and going off to the couch.
When I had 2 partners and both were spending the night, I was really glad I had a guest room. I'd spend the night with whoever cared more. My bf then slept like a rock, and went to bed earlier than my gf. So, I'd get in bed with him to tuck him in and have a short good night type conversation, or for sex. Then if I wasn't sleepy, I'd get back up and spend time with the gf, and then sleep with her.
Maybe that was TMI for the OP, but it's always interesting how different people share sleep, or not.