Cousins

When I was around 11 years old I went to stay with my cousins for some time. There were about 8 of us total all around the same age 2 girls and 6 boys. I was new to the group as the other cousins were accustomed spending time together. They introduced me to a "game" they all played. One night when the adults were having a get together they sent us upstairs to be out of their way and one of the girls said let's play the game . And there was a small debate about me being present, I was made to promise not to tell and I agreed. The two girls raised up the back of their skirts and two boys got behind them and started grinding their naked penises between their asscheeks.
They were mimicking how the adults were dancing downstairs two by two we all grinded on the girls until we came on their asses. This happened basically anytime we were left unsupervised. For years I think we stopped when we were all around 15. We never talk about or acknowledge what we used to do all those years ago.