Can’t overcome the guilt…

My parents are the youngest in their family. And that’s why Me and my sister are also youngest in all of our cousins. When I was child, like 8-9 years of age, my cousins and colony friends were of 14-15 yrs age, and they had just hitted puberty. So, hormones made them blind. I was young, and at that time they taught me some things that I shouldn’t have known at that age. They made me have physical relation with my own and only sister which I did because I didn’t know the severity, absurdity of that thing. I did that till 13-14 yrs of age. But later, when I started to grow mentally, I knew that this was wrong, And I stopped it. It was never without her consent but still, it isn’t right. But now, after 10 yrs, I am getting guilty thoughts about those things, which I have stopped since then, and I don’t know how to remove these thoughts from my mind or we can say, How can I redeem myself…? 😓