Sister and I overheard our parents and decided to have our own fun
During a family vacation, our family booked two rooms. One for the parents, and one for me and my elder sister. We checked in about 8 PM. Had supper. Changed clothes. We were just relaxing with our phones and then fell asleep.
Suddenly, my sister woke me up as quietly as possible. I tried asking why she woke me up but she closed my mouth with her hand and asked , "Can you hear?"
I tried to hear something in the silence. It was the sound of two people kissing and breathing heavily from the next room. The room our parents stayed in.
My eyes went wide open, and sensing that, she started giggling. We got up to the side of the wall and placed an ear on the wall. The sounds were getting more intense. Dad was saying things like, "You dirty slut."
A minute or so later, she started moaning. Super loud moans. She wasn't trying to be quiet at all. The clapping sounds and the moaning sounds made me so hard (although I was actively trying not to imagine my mom). My sister must have been equally horny. Her nipples were poking through her top and she was lost.
During the whole time, I resisted myself from touching my cock. When we occasionally made eye contact, we just made an embarrassed smile. After what was presumably mom's climax, they went quiet.
I was so hard because this was the closest thing to sex that I had ever witnessed in my life then. My sister who was lost and silent during the whole thing finally spoke, "I can't believe these guys." I just awkwardly nodded and tried heading to the restroom.
"Are you gonna jerk off?" she asked, quite comfortably.
"What no? That's gross," I said.
"Ah, okay. But it was hot, that's why I asked."
"Whatever."
So I obviously could not do it and headed right back to the bed. It took some time but I lost the erection.
"I'm cold, can you cuddle me?" She asked. That was nothing out of the ordinary. We used to cuddle all the time. So I went closer to her, and became the big spoon.
I could not get this out of my head, but I gradually fell asleep. Minutes later, she woke me up.
"You are hard. You are poking my back," she said.
I was embarrassed and backed away.
"No, I did not mean to weird you out," she said as she came close. "I am horny too."
"Ohh!" I did not know what to reply.
"Can we just feel each other up?" she asked hesitantly.
I wanted to. But I was hesitant. Eventually, I gave in and said, "Okayy."
We were now chest to chest, and she was hugging me tightly. I ran my hands under her top to caress her back, waist, tits, while her hands were exploring all over me before coming to my dick.
I slipped my fingers inside her shorts. Boy, was she wet?! I wanted to kiss her, so my face went near hers. We started making out. She was warm. Her body, her face, her neck, even her mouth. We got up, and sat in a more comfortable position to make out. We undressed. She was hot. I was leaking precum. She collected it with her fingers and tasted it. She started giving me a blowjob until I came on her tits.
I wanted to fuck her, but she insisted on me eating her. So I did. I buried my face in my sister's pussy. She did not repeat mom's mistake. She was barely vocal. I wasn't sure if she came but she pulled me back to her face and kissed me again.
"This is just a one time thing okay?" We should not do this again."
I felt the same. We cleaned up, and cuddled naked until morning.