My sister in law (wife of my wife’s brother) and I had been seeing one another on a regular basis for about two years. What started out as a bit of fun on a sporadic basis had turned in to a twice a week fuck-fest, mainly at her house as her husband was working during the day so we had the whole place to ourselves. One weekend my wife and my sister in law (sil) were working at the pub which was owned by my wife’s parents. Finishing time on a Friday was normally about 12 and by the time they tidied up and got people out of the door, it was normally 12.30 in the morning. I was at home looking after our daughter as I didn’t enjoy working in the bar that much to be honest. It was just a hassle after a hectic week at my own job and you also had to put up with some real pain in the necks, who were worse for wear. On this particular occasion, my sil was staying at ours as her husband had decided to do some night shift, so after the girls had finished up at the bar, they came home. All through the evening my mind was running wild, figuring out how I could get a quick kiss or a grope without the wife seeing. This proved not to be a problem. We sat down had a cup of tea and chatted for a while. My wife started to tidy up the cups and take them through to the kitchen. I seized my chance and stole a quick kiss from my sil whilst at the same time, cupping her pussy in my hand and giving it a quick rub. My wife returned from the kitchen and we sat and chatted a little bit more before we retired for the evening. After about 15 minutes, my wife was quite quick to fall asleep as she had been working all day. I on the other hand was thinking about what was lying next door in the spare bedroom with only a satin night dress on. I tossed and turned but all I could think about was going through to see my sil. I crept out of bed slowly as not to wake my wife up and walked along the top landing to the spare bedroom door. It was shut so I slowly opened it and slipped inside. My sil was lying awake and looked at and in a whispered voice asked what I was doing. ‘Coming for a cuddle’ I replied. ‘What if your wife wakes up?’. I giggled a little and said ‘not a chance, she is out like a light’. I sat on the edge of the bed and leaned across to give her kiss, tasting her lips and smelling her perfume. My cock was begging to harden due to these factors and I was unsure as to whether I should just get up and go out of the room or stay and progress things further. My brain in my dick won over and so I pulled back the covers and slid in beside her. She was in a panic and didn’t know what to do. I reassured her that my wife would not wake up and that we would be okay. I continued to kiss her and she eventually began to relax and to respond to my advances, allowing me to rub her rather small tits through her nightie. To move things along I took one of her hands and placed on the outside of my sleeping shorts to let her know I was hard. She took the que and pulled the front of my waistband of my shorts away from my body and took hold of my hardness, slowly rubbing it up and down. I progressed to run my hand down her body, cupping her pussy in my hand. As she continued to toss me off, I slipped a finger into her working my magic on the front wall of her pussy. She was bucking against me forcing her pelvis onto my hand. We continued like this for a good few minutes getting each other worked up, knowing that my wife was on the other side of the wall (thankfully not the headboard side). Our walls were made of lath & plaster so they are quite good at insulation. Not that it mattered as we were both very quiet during our petting session. I couldn’t take much more as I was getting worked up into a frenzy and made a move to lie on top of her. She in turn closed her legs and attempted to push me off with little success. She kept on saying what about your wife, but by this time there was only one thing on my mind and that was offloading my come into her. I told her that I only wanted to lie inside her and that we would need to be very quiet so she relented, opened her legs so I was in between them, took a hold of me and guided my hardness into her. Measuring 7” when hard, I think I am no bigger than the next guy, but the few women I’ve been with have all complemented me on my size saying it’s bigger than most, but my sil had had me a few times before so she knew exactly how to handle me and what to expect. We lay there but the inevitable happened and I started to push back and forth into her, but the only problem was that the bed began to make a slight squeaking sound, which made us stop. This happened a few times and I eventually got up out of the bed, took her hand, laid her on the floor and then resumed my position between her open legs. Again I slid into her and this time we were able to get into a significant rhythm. I could feel my cock sliding out almost all the way before I drove it back inside her wet warm cunt. She in turn was trying to pull me in deeper and whimpering softly as we thrust back and forth. I was getting close to coming and I asked whether I should finish off into a tissue or I should go ahead and fill her up with my spunk. The way she looked into my eyes and simply said, “I want your spunk in me, don’t you dare take it out”. With that I gave a few more thrusts pushing myself into her as far as I could and then shot my load into her. I lay there motionless with my entire body rigid as my cock pulsed and pumped my spunk into her hot pussy. The old panic alarms then set in and I had realised that I had just fucked my sister in law within 10 feet of my wife, although she was on the other side of a wall. I got up passed some tissues to her and then gave her one more quick kiss, sliding a finger inside here to see how sticky & messy she was before I left the room. I made my way downstairs and sat downstairs for a while until I calmed down and was able to clean up a little bit. Returned to my bed, where my wife was still fast asleep and then went to sleep. Sometimes at the weekend I get an additional treat of sex first thing, thankfully she didn’t want it on this occasion as I’m sure I still had the smell of my sil on my cock. Let me know if you interested in hearing about some of my other get-togethers with my sil as there are plenty to talk about.