My fetish includes both humiliation in seeing your mother getting fucked and getting raped by her, while tied down. In other words, the son is attacked by his mom and friends/bullies, stripped naked and tied to the bed. Then he watches his own mother as she sucks him and rides him, all the while all of the bullies surround them. She sucks their cocks and lets every one of them to fuck her ass. The son is forced to cum many times, and not only he gets to feel his mother's pussy, but also the giant cocks of his bullies as they brush along his own, much smaller one, through the perineum.
Here are my own 2 stories on that subject:
https://www.literotica.com/s/sons-friends https://www.literotica.com/s/candices-lust