I remember an experience I had once camping with parents and sister, I would have been 16 at the time and camping in Cambridgeshire.
We were at our usual campsite for a long weekend camp and I had got very friendly with the daughter of the family in the tent next to ours.
I had to share a tent with my 13 year old sister which was in-between my parents tent and their tent.
One night at about 1am I was still awake and suddenly heard the tent zipper opening, I put a torch on and see the girl from next tent coming in to my tent, then see she was only wearing a skimpy pair of panties and no bra.
It was a hot night so I was naked which was the norm anyway and only had my sleeping bag draped over me, she came up to me got under my sleeping bag and snuggled upto me and whispered in my ear that she wanted sex with me, she then took her panties off and started rubbing my now very hard cock.
What about my sister next to us and our parents so close I said, I'll be quiet she replied before going down and taking my cock in her mouth and giving me a bj for a bit.
She then got astride me and lowered herself down onto my cock taking it right into her wet pussy.
She rode me like that and was moaning quite a bit but fairly quietly, my sister stirred a bit and I thought she was going to wake up, but she seemed not to.
It wasn't long before I shot my load deep inside her pussy, she carried on pumping up and down on me for another minute until she let out a loud scream as she orgasmed herself, she sat on me for a bit while her body settled down before getting off of me and letting mine and her juices dribble out of her faping open pussy onto my pubes.
She then went back to her tent but as we found out when my sister and I got up she had left her panties behind and my sister found them and said oh she has left these behind.
Then to top it off I got out of our tent totally naked and was asked by my Mum what happened last night pointing at my pubic area, I looked down and see that my pubes were matted together with our juices still.
My sister the little tell tale told her that I had sex with the girl in the next tent.