Years ago I knew a guy, he had a 3 bedroom apartment, he had a (guy) roommate. All good.
About a year later a girl moved into the extra bedroom, they split everything three ways. I thought it was a little weird but I wasn't involved.
Come to find out it was like a poly deal, they both had sex with her whenever anyone wanted. Sometimes one guy would go into her room for a while then go back to his room to sleep. Sometimes she'd hit up one of the guys. Many times one guy then the other, sometimes a three way. I remember thinking this girl is getting the ******* fucked out of her.
She wasn't all that good looking but why not ?