My wife invited her sister and mother to visit and stay with us, for a week. We picked them up from the airport, greeted with the customary bus and cheek kisses, and drove them to ours. After the first night her mother decided she wanted to go and stay with other family she hadn't seen for a long while, so I happily dropped her off (not too far away). My wife and her sister get on great. They're like two peas in a pod, but for me they're a real nightmare, always laughing and larking about, like children, so I tend to just leave them to it. After a couple of days my wife and I were lying in bed, basking in the warm afterglow of a nice sex session, when she started telling me of her sisters boyfriend woes. Tbf she doesn't have a great history with men. Either arseholes, drunks or booked that just don't treat her very well. I was told she was missing intimacy most of all, and I couldn't wait to offer my services. My wife told me I was an animal and it was out of the question, but I explained that it made perfect sense. You know she would be with a bloke that would treat her nicely, isn't as dodgy as some of the men she has had run ins with and most of all.. Clean. I left it at that and went to sleep. I woke the next morning to find she had already got up, and I was lying in bed alone, naked and sporting a little morning wood which could have done with a little attention lol. One quick pic and sent on WhatsApp informed my wife I was 'up'. I heard footsteps on the stairs, so lay on my back, duvet thrown off the bed. The door opened and there was my SIL. She looked and stuttered about being sent up with a cuppa. I guess my wife had not shared the pic, just said I was awake and asked to water me. I got it off bed and took her by the hand, gangly pulled her towards me and told her not to worry. We had discussed it and it was OK. I heard the front door close, my wife had gone out now things had been sorted. I put the cup on the bedside table and leaned in for a kiss. Not the same as at the airport, but a nice one. With tongues and hands wandering. Her hands had found their way down to my much harder cock, and was gently stroking it. She whispered it felt nice. We lay on the bed, kissing and striking each others bodies. We have each other oral sex, she had a couple of orgasms, and we had sex. The first was kind of animalistic. Mostly just me claiming her pussy as mine. The second was much more gentle. Almost love making. We shared a shower and soaped each other, afterwards. A really nice mornings activities. My wife came home just after 2pm, though I was out in the garage so didn't see her until a little later. She said her sister had thanked her and said it had scratches an itch that needed seeing to. I said it was my pleasure and if it was OK I would be at her disposal for the rest of her stay. My wife said that was fine, but don't get used to it. My cock was still hers and always would be, though it's ok to lend it every now and then. And as much as I would have liked it, there would be No 3 we...... We'll see lol