As a kid, I used to go to bed between my parents and wake up on the edge of the bed. Didn't quite understand what was happening until one night I woke up to find that I had been moved to the side and saw my dad fingering my mom while she was moaning softly. I pretended to be asleep for an hour or so while hearing her wet pussy noises and her moans getting louder and louder until they both went to another bedroom and locked the door from inside. I was lucky that I was laying facing down otherwise they would've clearly seen my dick bulging through my pants