I wasn't going to share this but really enjoyed thinking about it so hope you will enjoy reading about it.

After about 2 years of almost none stop innuendos and flirting my SIL was staying at my house the night before we went to Alton Towers. I was about 25 I think and she was 21.

My wife was at work in a pub and my daughter was at her grans house so me and SIL were in the house on our own. She had a cute floral print summer dress on with thin straps and a bra with no straps.

We had been laughing and carrying on she told me that I had an eye lash that was driving her mad and she wanted to pluck it. I told her no way and we started play fighting. I was sat on the couch and she kept leaning over the side of me trying to get to my eye lash. Her last resort was to straddle me trying to pin my arms but pushing her breasts into me. Her bra started to slip down as we play fought and the strap fell off one shoulder showing off her breast. My God it was so perky and her nipple was rock hard.

I feel my cock starting to get hard and I'm guessing so could she. She started to grind on me just a little bit harder. All that was between us my my shorts and what turned out to be a very cute lace pair of knickers.

After what seemed like ages but was no more than a few seconds she leant in and kissed me. Her lips were so soft I couldn't help but kiss her back. I slid my hands all over her and within minutes she was straddling me wearing only her knickers she stood up and dropped them to reveal a nicely trimmed bush and what looked like a virgin pussy.

I pulled my shorts down and she got on top of me. She had no idea what she was doing but slowly got into a rhythm and started to moan as I pinched her nipples and ran my hands over her naked skin.

I didn't mean to but I came inside of her. She was a bit shocked but didn't seem to mind too much. We cuddled for a bit and kissed. I didn't want to let her go in case I never got another chance with her. She then got off me, went to the bathroom and got changed into her pyjamas.

I got dressed and sat there in pure shock at what had happened. It was the beginning of a long affair which I do not regret at all.