My wife travels often for business and as a result I often take matters into my own hands. I had gotten home from work and did some yard work. I had been spying some teenage girls at the neighbors pool and I was rock hard. My sister in law is staying with us as her husband in in the army and overseas. My sister in law is about 4 months pregnant with fantastic tits and a great ass both of which are more plump and rounded due to her pregnancy.
I decided to shower and masturbate. I enjoy prostate stimulation and I took my wife's hairbrush into the shower to play with. It has a gel handle and is curved just right. With the shower running on my back I slipped the handle up my ass and until it hit my prostate and then I started to work it back and forth. With my other hand I covered my cock and balls with shampoo and worked it into a lather. I started to tease my cock head with just one finger and waited for the tension to build as I fucked my ass with the brush handle. All the while I fantasized about my sister in law and how I'd like to fuck her between her huge pregnant tits.
I couldn't take it any more and started stoking my cock and bucking my hips with each stroke. The shower has a clear glass sliding door and I held onto the door with one hand and stroked myself with the other. I started to moan and felt that this was totally erotic.
I let out a loud OHHHH! and shot a tremendous load which hit the glass door. Due to the prostate stimulation my ejaculation of sperm was huge and flew out as a stream and ran down the door.
As I opened my eyes and came back to my senses I saw my sister in law standing in the bathroom. She was beat red and mumbled sorry and turned. She proceeded to fly out of the room. I'm not sure how long she was watching.
I toweled off and put on a robe. As I walked down the hall and past the bedroom my sister in law was using. The door was closed but I could hear the bed squeeking. I'm sure she was masturbating. I could imagine her on her back fucking her fingers and rolling her hips. With the amount of noise the bed was making I'm sure she was into it. I tried to open the door to return the favor of seeing her but it was locked. I heard some stifled squeals and moans as she was probably cumming. I didn't see her then but later is another story.