Accidently Blackmailing Aunty

I'm not from a well off family, but do okay gardening and odd jobs for for well healed. My aunt Katherine 47 married into money and had 2 children who attend high a price University and so she is home alone as Paul 55 her husband works long hours and plays golf on weekends here or away somewhere else. He gave me the job doing his garden as I'm family, I'm Morris 24 and my parents live on the other side of the city from Katherine. My father John use to call his younger sister Kathy, but she hates that and so we all have to call her Katherine now. When Katherine married Paul he had her sign a prenup and so if she does anything wrong she get nothing. Katherine as I found out loves sex and was playing up on Paul because he was never there or playing golf instead of fucking her. I came over to trim the hedges as Paul likes them no more than 5' high and so I trimmed as usual. I noticed a car parked at the back of the garage, that was strange as they are usually parked out the front. It wasn't a problem as there's a concrete driveway out back also and you can drive straight the garage an out the back of the property as there's doors front and back. No real concern of mine and I kept doing my job, than as I was passing the back of the house I saw a stranger fucking Katherine. They were both very busy having sex and didn't see me, so I filmed them fucking. Don't know why, I just did on the spur of the moment. By the time I finished my work the stranger was gone and Katherine was drinking on the patio. I said hello and kept going and left shortly after. I watched the recording later, but than had a date with my girlfriend Suzie 22 like me a high school dropout and works at our local supermarket, as usual we had a good time and had sex with her staying the night and me dropping her at work next day. I saw the stranger's car at Katherine's home the next week but all wasn't well. They argued and he left and she was in a bitch of a mood after that, but Paul returned home just before I was to leave. As usual we had a chat and then he went inside I left and picked Suzie on my way home. Suzie is moving in with me soon and we're thinking of marrying in June. Katherine was in a bad mood the next time I was over there moving. She had a go at me over the noise the lawnmower was making, I forgot myself and said sorry aunt Kate I'll take away from the house as soon as I can. It was like throwing petrol on a fire and she went mad at me, calling me useless and worthless and a few swear words besides. I also got angry and said I don't fuck strangers and betray my partner. She started to call me a lair and I showed her the video of her fucking the stranger and she shut up and went inside the house. Any I cooled down and was going to delete the video and say sorry to Katherine. After finishing the mowing I went to the house and she was crying in the lounge room. I said sorry, but before I could say I'll delete the video, she asked me what did I want. I said I don't want anything and again she asked you must want something, money or is it sex you want. Katherine is a gorgeous woman and I said I don't want your money. With That she started undressing and said alright you can fuck me and I was lost for a reply at that moment and also got a hard-on. So I fucked Katherine, I was a little awkward the first time. But she wanted me to fuck her again. After the fuck I showed the video and deleted it in front of her and expecting that to be the end of it. But I was wrong Katherine and the stranger had broken up and she was without a lover and as I had fucked her and she must have enjoyed it. Every time I was there she wanted sex with me and I even got called over just for sex. Best thing was that me being there didn't attract attention from the local busy bodies and I could out front. She even had sex with me in the garden shed as she couldn't wait for me to finish my work. She also convinced Paul to buy me and Suzie a house for our wedding present closer to their home then where we were renting. Suzie doesn't know I'm fucking my aunt, nor does Paul.