when I was young maybe about ten, my next door neighbour was a guy and a couple of years older than me. Our parents let us watch what we wanted and over 18 films, that probably contributed,
He used to try and force me into things, like hed say "just in and out once" and get me to touch his bits (which I remember being all gritty strange) when his mum was watching me and my brother.
We would play outside and build huts in bushes and he would knock me to the ground and I always resisted with him on top. But the next day I would get myself in the same position and go out and play with him being coerced into a dark shed, where he would plead to do adult stuff. Sort of explains how my ex convinced me into being so conformative but that's a different story,
I may have been younger when it started.

The thing is I FORGAVE him. I never held it against him. I actually slept with him while he had a longterm girlfriend and I had a boyfriend. when I was 17/18. I was hesitant to kiss him and we stopped halfway . It was wrong and I did some things I'm not proud of at that age cause I became really self destructive at that age.

But I don't hate him, he was a young man and he has a wonderful family now and he deserves it.

Chances are your sis understands that you never realised the magnitude of what you were doing. I don't know if you should ask, prob not. People forgive its a sign of maturity...