So my Mother in-law was living with us for a while there. She is of good shape, blonde hair, slight tummy and nice big busty tits. 

With having some nicer weather of late we decided to tidy the garden. She was wearing a thin strapped top and shorts. I first noticed her curvaceous arse as she was bent over in front of me. Being the pervert i am i was looking for her panty line as i would in any situation with a hot female in front of me. I did manage a few glimpses up the baggy leg of her shorts to the top of her legs. I also had to watch on as those big busty boobs were being flashed at eye level whilst we were doing the garden. This was quite the turn on and i used these mental images for a few wanks later on.  A few nights later the wife was upstairs in bed early and my Mil and i were downstairs watching a movie. She was a few seats along on our sofa wearing her pyjama bottoms and another strappy top. I myself was not long out a shower so i was in my loungewear, shorts and tshirt. About 10 mins into the movie she unhooked her bra strap and took it off from under her little vest top. This again gave me the horn and I couldn't help but stare at her big nipples poking through her top. This had me sitting with a semi. I'm sure she didn't mind as the few times ahe looked she caught me staring she just smiled. 

I then got up to go to the kitchen unable to hide my bulge in my shorts, i'm sure she would've noticed especially as when i got to the kitchen i had a few pulls to make it obvious and bigger.

That night i was fucking my mrs when the image if her mum came to my head. I was picturing her at our door watching us fuck saying it was ok and to continue. She then pulled her tits out over her top and started pinching and twisting her nipples. She then let her dressing gown fall open to reveal her pussy with a neat patch of sandy coloured pubic hair and tan stockings that went up to the tops of her thighs. Her pussy was glistening with wetness and her lips were shaped like butterfly wings... not long after this thought i shot my cum powerfully in to the wife.. 

would love to hear if anyone has had any similar experiences and equally dirty thoughts...