Caught my aunt Jessica having sex with a guy who wasn't her husband eighteen months back. I'd gone round to collect a sports bag I'd left there after training two days earlier, and found her taking this guys cock from behind. She tried to make out it was all innocent and that it would only cause trouble if I told my uncle. The fact was I already knew my moms youngest sister was and is a slut, so I just said "Yeh whatever". That same night she text me and pleaded with me not to say anything, then text "Call by tomorrow and I'll make it up to you".
I was round at midday knowing her husband was out playing golf. After practically stripping then dragging me into the shower, Jessica dropped down and sucked on my cock for a hell of a long time. Then standing up with my cock aching to be inside of her, she turned around and said "Fuck any hole you want". I was so turned on and had never before had anal sex, so without even thinking about it, I rammed my cock up my aunts asshole and loved the tight feeling of her ass surrounding my dick.
We fucked and fucked and fucked some more. Going from the shower to her and my uncles bedroom. In those two hours, I learned more from my aunt than I did from all of previous girlfriends put together.
And it's carried on right to this day. Jessica told me, whether she was just trying to please or not, that I was one of her best ever fucks. And since then my aunt and I have had sex pretty much two to three times a week since. It would be more, only her husband has changed his job recently and he often now works from home. Even so we still find time when he plays golf, or when she visits her sisters each week.