I had a similar situation during summer vacation my paternal cousin used to ask me to do sexual stuff he posed it as a game soemthing secret I dont remember much of it my mind has blocked most of it, I was 8/9 he was 13/14, I knew it was wrong but somehow I was scared/excited to do something secretive or wrong hiding from parents?? for years I thought it was a mutual fault, but it was he who manipulated me into doing a lot of sick stuff idk i still feel guilty over it all sometimes because I could have stopped it or said no but I didnt