Having a Quickie

I'm Leonard 26 and live with my sister Kath 29, neither of us are centerfolds. But we do have fairly good luck dating. But sometime it slows down and you don't have a date or the your date cancels at the last minute. On one these times my date had to go away has her grandmother had gotten really sick. Kath regular guy had to work the weekend so the job could be finished on time. This left us both sitting at home with nothing to do, I suggested we go to a movie to break our boredom. Kath wasn't interested in doing that and preferred to stay home. I asked what did she want to do and she replied get laid, I decided to tease her and answered okay let's fuck. She got a shock look on her face and then said your my brother. I kept it going to see how long it would take her to blow her stack, saying so your on the pill and so you can't get pregnant. I expected her to explode, but she stayed silence. Then she shocked me by saying okay we'll have a quickie and see how it goes. It was my turn to be shocked, I was about to tell her I had been joking and then thought it was her trying to get me to back down. So I responded by saying okay your bed or mine and waited for her to back down. She simply replied my bed and she got up and started undressing as she headed towards her room. I started to follow her thinking she was still waiting for me to back down. She wasn't, she was very horny and we had our first quickie and I really enjoyed it. She said I needed to improve the next time, later we fucked again and it has now become a regular thing for us to fuck. We both still date and have sex with our dates. But sex between us is the icing on the cake you could say, as neither of us are in relationships that look to be going anywhere at the moment.