I was 15 at the time and my brother (17) and sister (14) went fishing with my mother and friends to a isolated beach. They headed off to a rocky point and we could see them in the distance as they started fishing. There were many rocky pools close by so we went swimming and diving around them. My brother had a great body as he did a lot of work around our farm and had a great looking cock as I had caught glimpses of it around the house. We used to grab his towel sometimes as he headed from the shower to his room which always left him naked as he scurried off.
Anyway we swam for a while, caught some sun on our towels but then got a bit bored so we decided to wrestle in the water. Well my brother was wrestling with my younger sister and I couldn't help but notice the obvious bulge in his shorts. I was so excited but didn't know what to do. They were both getting into it when he suddenly ripped her bikini top off. They stopped as she tried to cover her boobs with her hands but then he grabbed her bikini bottoms and pulled those off. She didn't know what to cover but I couldn't stop staring at his cock as I thought it was going to burst from his shorts.
I decided to help her and jumped on his back. He was too strong for me and next thing I knew I had lost my top but didn't care as it was too much fun. Lots of times I felt his cock pressing against me so when I had a chance I slipped my hand into his shorts and grabbed him around the base. I will always remember that feeling. It was so big and hard and hot. It only lasted a few seconds but felt like mins before I released him but for him it was enough. He stammered something and got out of the water and head back to our car. I didn't know what to do but I was so wet and felt so horny.
After a few minutes I followed him to see if he was ok. I found him naked in some sand dunes masturbating and as I secretly looked on he came in a matter of seconds. His cock was gorgeous and I wanted to feel it some more but didn't have the courage to say or do anything. I know he was relieved but I was still so wet. I always wish something more had happened.
Later in life we had some other experiences but all part of growing up I think and could of been more for this horny girl.