My cousin was a year younger than me at the time, and we were out with our mums at a summer fair of some sort and it was pretty busy.
We went our own way from our parents and mooched about when I said I said I needed to go for a wee, we found our way out of the crowd and in some large bushes well out of the way, I started to get an intensely sexual urge for some reason and while she wandered nearby I shouted her to come closer cos I couldn't do it without her keeping watch closer by.
I don't know if she knew already but by the time she got nearer I had a full erection and was masturbating, as she got within seven or eight feet away she could see me and I was wanking away totally rapt by my cousin seeing me from from so close, she was looking round keeping watch and I said come here a minute and as she turned to me again my come started to actually pour out of my dick, quite a lot and she could see it clearly. She seemed a bit worried about someone coming or maybe what I was doing and I suddenly got paranoid I could have been seen too. Nothing was said after this either and never mentioned it.
On another occasion we were in my bedroom alone during the day, her mum was visiting with her. I just got back from school and this sexual thrill got me going again and I decided to change my pants in front of her, she covered her eyes but I pretended the pants button was stuck so I pulled them down along with my underpants and had my really hard dick sticking out in front of her, she started looking through her fingers and said ohh!. Not a massive reaction but doing it was an intense turn on.
When we were much younger we bathed together, I said should I wash you and I washed her then said to 'go on your knees so I can wash you underneath' and she did and as the bubbles slipped down her bum and the backs of her thighs then I could see her fanny from behind and her bumhole, I squeezed the sponge and flannel over her backside then gently wiped her there then I did it with just my fingers, she never said anything so I carried on, I slowly rubbed her tight anus and slid soapy fingers under her along her smooth pussy and her groin, I even leaned forward to smell her private parts I got a scent of her there that made me feel dizzy.