I'll apologize in advance for the long post, but I am bearing my soul, and sharing this for the first time.
When I was a young, curious, confused teenager (prolly 15 or so, maybe a bit older) I made the mistake of letting my curiosity get the better of me. Twice I felt my younger (by 2 years) sister's vagina in her sleep. I sort of touched around, by the opening and a little bit in the first time, but not the second (like to your first knuckle from completely outside, but she was still a virgin, and I don't think i was doing it right anyway, so i wonder if it was even penetration). I never tried to give her pleasure, to kiss, or to lick, never touched her clit, and I never jerked off or even played with my penis or touched her with it. The second time, she woke up and said "gross". I feigned starting awake from her response and asked what woke her, to which she just went right back to sleep.
Perhaps a year or two prior, we had both been curious about the other sex's body, so we would innocently show each other and do the same with our 2 best friends. Puberty makes kids do silly things. I did notice that she shied away from it first. Actually, we were pretty open with each other about our private parts as children, and didn't really see anything wrong with running around the house naked.
I am 24 now, and I have ever since been filled with guilt and regret over the whole situation. What made it worse was that both times were when we were sharing a bed on vacation. I feel like I have totally failed her and violated her trust - as a big brother, family member, and a friend - and have sullied the sibling bond.
I don't know if she remembers any of it, or how it's affected her; we'd always had a strained relationship as kids and I thought she didn't like me anyway before that, so any negative emotion was not particularly new. She has never confronted or talked to me about any of it.
We're both adults and graduated from college now, and it seems the our relationship has turned a total 180 in the past two years. I am very happy to get to connect with my sister and have a positive, mutual, respectful relationship with her that we've never had before. However, this incident lingers in the back of my mind always, and I feel like such a horrible person, brother, and man for doing it in the first place and for having never owned up to it and apologized to her. I have been working myself up to it and just putting it into the open with her.
I don't know what would happen because of that. I would not hope for forgiveness, but only an understanding that, curious teenage boy i may have been, I know what I did was wrong and am truly from the depths of my soul sorry for what I've done and how it might have affected her; that I've been truly sorry from the moment it happened; that, despite our strained childhood, i always wanted deep down for her to be my best friend; that I have always worried for her and loved her.
I don't know how sufficient this is, and I won't speculate to, as in the end, the judgement belongs to her and her alone. All I want to do is clear the air between us, to let the truth be told, to accept responsibility for my actions, and for the both of us to be able to move forward in life on higher ground. Of course, I want to keep my sister and our new mature relationship, and so I hope that she concludes that my self now is much different and truer than the me who did this to her in utter confusion and curiosity, but that is not my decision to make.
Make what you will of this, I do not mind. It has torn me apart for the last decade (? I honestly can't recall a date when it happened), and putting it into words has to be the first step towards admitting my faults and righting my wrongs to her.