My wife Sue and I are in our late fifties. Our kids have flown the nest so it’s only the two of us in the house. Our sex life was good but over the years it has become stale. Sue works as a teaching assistant in a local school And I am an electrician who works long hours . Several months ago I came home early from work as I was feeling unwell. As I put my key in the door I could hear noises from upstairs ? Sue wasn’t due home yet ? So unsure if we had burglars I quietly opened the door. As I slowly crept up the stairs and I became clear that someone was having sex ! I was expecting to see my wife Sue with some bloke ! The bedroom door was slightly ajar and I peeked in. I was surprised not to see my wife but her older sister Doreen . She was on her knees naket giving some black guy a blow job in our bedroom. Doreen and I have never liked each other ! They are more affluent than us as her husband has his own plumbing business and she like liked to let everyone know how wealthy they were! She didn’t work but simply spent her time shopping and pampering herself . But the posh bitch was now on her knees naket sucking black dick ! Doreen was a size 18 with DD breasts and these wobbled as she sucked this guys cock which must have been 8 inches long . I recognised the black guy who was a local cab driver I used before . He was a big guy about our age and over 6ft tall. With everything to match ! They were both oblivious to my presence on the other side of the door ! And I took out my phone and started to discreetly video them. The black guy got Doreen to kneel on the bed I could see that her pussy was shaven except for a landing strip . And he took her from behind slowly sliding his big dick into her . He fucked her hard and fast and the dirt bitch was loving it ! She moaned loudly and cursed as he pounded her pussy ! This was getting me horny and I took my dick out as I watched . He then pulled out of her pussy and ass fucked her as she squealed . He finished her off by getting her to kneel in front of him while he came over her lovely big tits . She rubbed his spunk into her tits and licked the the dribbles from his cock . I quietly crept back down the stairs before I was discovered and quietly when out the front door ! I did think to myself why am I creeping out of my own house when that slut is fucking in our bed ? I must admit it make me as horny as hell and I drove the car around the corner so as not to be spotted and replayed the video on my phone . I managed to get it all on video and it was better than any porn vid.. After about half an hour I checked around the corner and I seen both of them leaving and driving off. I thought to myself my wife Sue is obviously aware of this and maybe that black guy is also shagging her ? By now I had forgotten about feeling unwell and went back into the house . When Sue arrived home In was sitting having a cup of tea . She was surprised to see me and went quickly upstairs Obviously to check no evidence was left behind ? I didn’t say anything to my wife about what I saw ! But that night I couldnt wait to get her knickers off and give her a good fucking as I thought about Doreen ! The following weekend Sue asked my to help her sister Doreen put some stuff up in the loft as her husband was away in Newcastle on business . I arrived at their large detached house about 11am. Doreen as usual was in full make up and in her designer clothes . I put the stuff in the attic And she offers me a coffee . She was telling me about how her Rob works so hard running the business ! She made a point of showing me the new diamond bracelet he had bought her and telling me about their holiday in Barbados and asking if we had ever been there! This was a typical of Doreen been a bitch as usual , as she knew we could never afford a holiday like that ! She then said did I ever finish the decoration ? I replied did you not notice when you were there on Tuesday ? She looked a little shocked ! But mumbled I only popped in for a ten minutes to see Sue ! I said well you were there long enough to get your knickers off ! She said what do you mean? I took out my phone and played the video ! For once Doreen was speechless ! After a pause she said please don’t say anything to Rob ? I said it depends if you make it worth my while ? She replied how much money do you want to keep quiet ! I replied I don’t want your money Doreen ! She said then what do you want ? I scratched my head and said I suppose said I could post the video on the internet ? She said No No “ please don’t ! It will ruin my reputation ! I replied well I now see behind that facade of you been posh , that you are really just a dirty slut! I unzipped my trousers and pulled out my erect dick. She hesitated but with out saying a word she kneeled down and started to expertly suck my cock . I told her to get her tits out and she took of her top and bra . I played with her lovely big breasts which she was was enjoying and I stopped her sucking and placed my cock in between her tits . She cupped her breasts and give me a tit fuck . I couldn’t believe I had my posh bitch of a sister in law In her kitchen on her knees pleasuring me ! I ordered her to get her knickers off and bend over the kitchen work top ! Again with out a word she did as she was told . The sight of her bent down with lovely big ass and pussy exposed made me rock hard and I was struggling not to cum.! I played with her pussy and bent down to lick her dripping juices as she moaned She said I need your cock in me now ! I teased he pussy lips with my cock ! I said Doreen tell me how you are a cock mad slut ! I was really enjoying hearing the bitch telling me how she was a horny slut and need regular cock ! And that Rob couldn’t get it up any more ! I fucked her hard and fast And she moaned loudly . her love juices ran down my dick as she climaxed I pulled out of her pussy and And slid my cock up her ass hole ! She squealed and called me a dirty bastard as I ass fucked her! But she was soon moaning with pleasure! Before I was about to cum I pulled out and got her to kneel in front of me like the black guy did to her. I spunked all over her big tits and face . As before she rubbed the spunk into her tits and licked my dick clean . With a big smile on her face which was still splatters in spunk Doreen got up and said she was going to have a shower. I said I got to go , but I will be back next week for the same ! She laughted and said looks like I’m going to be a busy girl keeping you and the cab driver happy ! She winked ! well I won’t tell Sue if you won’t tell Rob ? With that she disappeared Into the shower and I let myself out . Doreen continues our weekly arrangement as Rob Is often away and as I presume she continues to be fucked by the black guy ! and the dislike I had for my sister in law has turned into a healthy lust for the horny bitch ! As for my wife Sue I never did find out if she fucked the black guy too ? But I have my suspicions as has regained her love of cock and now wants it every night and I’m not complaining ! So I’m kept busy servicing both sisters! Hopefully this will continue for many years to cum! The next time I get a taxi driven by that big black guy I owe him a large tip . .