I need advice

This is something I find very difficult to talk - or even think - about and have never discussed with anyone.

When I was young, myself and my brother went through a period of "messing about" (kissing, touching etc). I don't remember a lot about it because I think I have repressed the experience throughout my adolescence but I am now 20 and am really struggling with feelings of shame and guilt, as well as worrying how it may affect my brother. After looking into it, I would not describe it as abusive. We are only a year and a half apart in age and there was no element of force or anything like that, so I put it more down to sexual experimentation that I believe is more common than people think.
Despite all of this, I can't escape the feelings of guilt, disgust and shame that I could allow such behaviour to take place, even as a child (I think I may have been around 9 or 10 when it started and continued sporadically for the next few years). I remember reaching a point when I realised how inappropriate such behaviour was and trying to tell my brother that it was wrong and shouldn't continue. Please don't think I am attracted to my brother in any way or that I think this sort of thing is okay - I could chalk it down to many things but it was certainly nothing romantically motivated!!! However, as I am the older sibling I feel a deep sense of responsibility for what happened, even though I am a girl and he is a boy. I don't know who originally initiated what I think began as fairly innocent touching but the thought of it still repulses me.

I don't want to bring it up in case he does not remember it or isn't bothered by it. He is in a long term relationship and seems to be fine. We have a good relationship and our family is very close. I just want to know - am I a terrible person? Does this happen to people and they just don't talk about it?

You are not a terrible person and it is much more common than people think. Since there was no coercion and a small age difference there is nothing to feel guilty or worry about. Try to believe this and be at peace because it's true!

Would a terrible person feel such sincere and deep regret?

Would a terrible person have stopped because they knew what they were doing was wrong?

Would a terrible person even care?