Before i start - i dont have or ever had any incestious thoughts about my parents, neither before or after what happened. Ok, now lets go!
Soo the first time that happened was when i was on a vacation with my Parents. I was around 15, i think. My Parents were already 50+ at that point. We were in a hotel in tunisia and shared a room. I slept like 5m away from them on a seperated bed. We all went to bed and i was about to sleep in, facing the wall, my back turned to them. Then suddenly i heard a really, REALLY quiet creaking and squeaking. I was like wtf is that? I didnt even think about something naughty, i thought that it was something outside or so. After like 2 mins i slowly turned around and saw both of them laying on their sides, their backs facing me. Then it hit me like a bolt, and i thought "no way, they're fucking! Wtf?" At first i was disgusted, and then it started to make my dick tingle. I got hard and even tried to masturbate a bit, but that would have been too loud (the sheets and stuff) because they were also reaaally quiet. That went for like 5 min until my mom made a sound like she cleared her throat, what must have been the signal for my dad that she's finished. He got up and went to the bathroom, i guess to finish himself off because i heard the toilet flush after that.
The next morning they left for breakfast, and i was still stunned, shocked, yet amazed and horny for the sounds i heard. It made my heart race like crazy, i wasnt even brave enough to just breathe because i was scared to get caught. The fact that i had to lay there, hearing the bed squeak rythmically made me so damn horny in that moment. Felt so wrong, yet so hot to hear them.
Not gonna lie, the more i think about it, the more i'm sure that this wasnt their first time fucking right next to me since they were almost too quiet and we always shared a hotel room. Naughty parents!
And that whole thing pushed me into my kink for listening to sex, that kink is how i found this forum.