My Mother in Law is HOT

I'm Richard 33 married 3 children, We recently returned home from working overseas. We purschased a house next to my in laws. My wife Susan wanted to be close as her father Alan has cancer and is not doing well. Her mother Grace 58 is a gorgeous looking woman and looks like she in her late thirties. Susan is a fully trained nurse and got a job at the hospital where her father is being treated. I work from home and see Grace working in her garden a lot. Early last month I saw her playing with herself in her greenhouse, I got a horn in a instant and couldn't get the sight out of my mind. I even had it when fucking Susan and she looks like her mother a lot. But I started getting a hard cock every time I saw Grace. Over the following 2 weeks I saw Grace masturbating several times in the green house. She has a canvas deck chair there and it seems to be her perferred place to masturbate. I decided to approach her and see where it went. I knew routine and I went over and waited till she was really into it and walked in on her. She was shocked at first and then seeing my hard cock straining at my pant. She It seems I got you excited, maybe we can help each other out. I nodded and we went to her bedroom and I fucked her, this became a regular thing. Alan got released from last week and is in remission now. He is very frail and I'm still fucking Grace, I also got Susan pregnant again. She had forgot her pill, when Alan was very ill a few months back and we had sex to try and keep her mind off her Alan's condition a bit. Alan is very happy that Susan is pregnant and says it helping him recover. I haven't been getting a lot of sex from Susan lately, but Grace is more than making up for the deficit.