They had no idea I was there

After my parents divorced, my mother and I moved in with a guy she knew from work. I watched my mother numerous times sucking his cock on the couch as they watched a movie. She was so preoccupied with his cock, I was on the stairs watching. I could hear him moan while mom was sucking his cock so I knew he was about to cum.
He liked to fuck my mother bent over the couch and smack her ass asking her if she liked his big cock.
It was about two years later we moved out and mom bought her own house and left that guy.

Was this through a window? Under a bed? Done with mirrors?

In a park, by railroad tracks, through windows…