My sister Sal and I had trouble controlling our hormones around each other. She flirted quite a lot with me and was always checking to see if I was trying to hide a stiffy.
Years ago I saw her masturbating in the lounge, she was using a cushion between her legs and grinding into it, I went to my room and jerked off. A few weeks later we went with mum while she got her hair done and went to the beach as it is so boring waiting for her. We made faces on the sand out of seaweed and stuff and it was fun. We messed about and ended up covered in sand, Sal brushed me off and I swear she used it as an excuse to try and have a feel of me, I brushed her off and had the chance to rub the sand off her.
Then Sal said she wanted a piggy back so she jumped up and I walked along the edge by the water. After a bit she felt heavy but I liked her on my back so I moved my hands from under her thighs to hold her under her bum which was easier. As I walked on we chatted away and feeling her tight bum in my hands was nice, then I realised my thumbs were resting right on the inside of her thighs and against her crotch. My mind did backflips as I thought about her shorts riding up against her and I let my thumbs rest there for a while, as we walked they rubbed up against her slightly, I could feel her through the soft shorts she had on, any minute I was expecting her to yell at me but it never happened.
I knew I had started something, I could feel my cock throbbing in my jeans and I let my thumbs press a little firmer against the warm fabric of her shorts. A little bit further on she had stopped talking and I was flicking and rubbing my thumbs over the crotch of her shorts and feeling the softness of her pussy under the fabric, Sal was breathing quite heavily in my ear and had her head on my shoulder, her body had gone floppy but I felt her pushing into my back and spreading her thighs wider. My cock throbbed as I rubbed and prodded my sisters shorts, one thumb crept under the edge of her shorts and was poking the cotton gusset of her panties and I could feel her swollen lips against the material and some wetness. Then Sal began to squeeze her thighs and push against my thumbs. I rubbed her for all it was worth and suddenly she gasped and held me tight as she jerked on my back, I felt a stream of hot liquid fire from my cock and wet my jeans. Later she got off and smiled saying how it really tickled. I had to cover my jeans with my jacket.