The reason I'm confessing, is my older sister has asked if she can come and live with me for a short while. She also said if she can, she'll make sure I receive what I got as a kid and much much more.
As a fifteen year old kid, I walked in on my sister (She was eighteen then) being anally fucked by her boyfriend. They didn't notice me at first, so I stood and watched for about five minutes, seeing my sister cum as she was being fucked hard from behind. When they both eventually noticed me, my sister jumped up and made me go to my room. Ten minutes later it was her turn to walk in on me masturbating.
She made me swear not to say anything to our parents, then as a way of cementing my promise, she took my cock into her mouth and began to suck me off. It felt so good and I was about to cum when she stopped. Removing her bath robe my sister turned around and spread her ass cheeks. She told me firmly to fuck her in the ass.
My first attempt only ended up sliding my cock into her pussy. She jumped and said I couldn't fuck her there as she wasn't on birth control. Taking hold of my cock, she put it to her ass and I pushed in. I fucked my sister as I thought you should fuck someone. Basically like a piston. Unfortunately I didn't last long and busted my nut up her asshole.
She thanked me for fucking her and made me promise again not to say anything. Just before she left my room, I told her I wanted to fuck her again, at least once more not to say anything. The following night when my parents went out, my sister took me up to her room and had me tongue her pussy and ass. Then like the night before she knelt up and had me put my cock up her ass. Only this time I took my time, fucking her slowly at first, then faster as she began to shove back onto my cock.
My sister came first yelling at me not to stop. Not that I was going to. Feeling her asshole squeeze my cock I felt my orgasm rising and did something I'd heard about. I pulled out of her ass, moved up the bed and ejaculated all over her face and head. She told me off for ruining her hair, but I didn't care, I'd just fucked my sister.
It was four months later when I next got to fuck her. She was drunk and I took advantage. It wasn't the same though as she just wasn't joining in. I still busted my nut up her asshole though.
The thing is we're both different people now. She's married for one thing, even if they are going through a difficult patch. And I have a girlfriend. Family sex is really fucking fantastic though.