Had the same experience before. I was at my gf place together
with another couple who is our friends too. Four of us had a couple
of drink leaving us tipsy and decide to hit the sack in my gf room.
In the middle of the night, my gf started to caress me and i
succumb to the temptation and started having sex with her on the
bed while the other couple sleeps on the mattress on the floor.
Guess her moans might have been too loud and it wake the other
couple up. Seeing us having sex kinda made them horny too and they
ended having sex too on the floor. After the whole thing, we still
go out as usual though now i see his gf in an another light.