My wife and I usually plan at least one camping trip with the kids over the summer. This past summer however, was just so busy with activities that it was next to impossible to plan a camping weekend. For the last three years we have gone with my sister-in-law and her kids. Her kids are all the same ages as ours (we have 3 as does she) so they get along and play nicely. My sister-in-law is 41 years old (3 years older than my wife), and has a very thin body with nice tits (I'd guess a GOOD c-cup). She's been divorced for about 3 years now and hasn't had a steady boyfriend for about a year.
We had all planned to go camping on a particular weekend, from Friday early evening through Sunday. My wife was asked at the last minute by one of her friends to watch her baby. Her friend had nobody else and it was a situation my wife felt obligated to help - long story there. Reluctantly my wife agreed. Since we had all plans set and reservations made for camping, my wife insisted that we all go without her.
I worked a half day on Friday and my SIL had the day off so she drove up ahead of us. We arrived at the campground just in time to help my SIL setup her tent and then setup ours. Before we knew it the sun was setting and we were all sitting by the campfire. The 4 older kids (ages 11 and 9) wanted to all sleep together in one tent, so we agreed that they could have one tent and I would share the other tent with my sister-in-law and the two younger ones (ages 6). My SIL had two queen air mattresses setup in her tent so I ended up sharing one of the queen mattresses with my youngest while my SIL shared hers with her youngest.
The next morning the kids were up early, too excited to start the day. We spent most of the day at the beach swimming and just having fun. We packed lunches and then bbq'd for dinner. As the sun lowered in the sky, we headed back to our campsite and everybody washed up before relaxing by the fire.
Even though the day was fun, it was nice to finally get back and relax at night around the camp fire. I had packed a frozen jug of mixed drinks, just in case. I was surprised that my SIL was happy I had brought the drinks, as she's not much of a drinker. The kids were all having fun so we let them stay up a little later, knowing that it was our last night there.
Eventually everyone was tired and ready for bed. The two little one's heard that the older kids were able to sleep together and of course they wanted to as well. My SIL said it would be "OK" but that meant that her and I would have to share a queen mattress. I've always had the fantasy of f***ing her, so you can imagine I was totally "OK" with it also.
My SIL wore a pair of loose fitting shorts (g-string under - I could tell because she whore white shorts) and t-shirt to bed. The night was cool and it felt nice sharing the warmth under a blanket with a stranger. Even though I was tired, I had a very hard time trying to fall asleep thinking of my SIL lying next to me.
Maybe a half hour had passed and all was quiet as everyone was fast asleep. I was in a sleepy horny haze and thought I'd take a chance. My SIL was sleeping on her side facing away from me. Although a risky move, I rolled over onto my side and slung my arm around her pressing my body up against her back. If she said anything I could pretend to have done it in my sleep - I've done it with my wife plenty of times. To my surprise, there was no reaction from my SIL.
I laid there up against her, just feeling the warmth of her body against mine. After several minutes I shifted my body a little so that my hand was under her arm and cupping her breast. She moved a little but said nothing.
As you can imagine I was getting extremely turned on at this point. My cock was growing hard and I pushed up against her . The smell of her hair and perfume along with the simple feeling of pushing into her bottom, felt good enough to bring me to orgasm. Had she been awake, she surely would feel how hard my cock was pushing up against her bottom. I gently pushed my throbbing cock against her bottom. I did this several times, just enjoying the feeling.
Then I felt her push back! Was she awake and aware of what I was doing? When she pushed back against me I though "Does she wants it as bad as I do?" I continued pushing up against her in a gentle subtle rhythm similar to having sex. It seemed like several minutes had passed when I noticed her breathing increased - mine probably as well.
It was at that point that I thought I'd go for it all the way. I reached down and pulled my shorts down just enough so that my cock was free. I then placed my cock so that it was poking my SIL's ass between her thighs - if the shit was going to hit the fan it would be now. Her reaction was to let out a long sigh and push harder back against me. I'm certain that she felt my bare cock pushing in between her thighs now, and still didn't say anything. For me, there was no turning back now.