Last summer my sister came to stay with my family for a week. We had not seen them since they moved abroad the year before for the sake of my brother in law's career. Thankfully, the killjoy had not come with them, as he could not (or would not) take the time off work. It made me sad as we had always been a close family, and now we all lived so far apart.
One particular hot summer evening, after the kids had all been put to bed my wife, me and my sister had settled down to watch the TV. After a while, the programme was losing my attention, and it occurred to me that my sister, next to me on the sofa, had been unusually quiet for the last ten minutes. I glanced at her and noticed that her face was quite red, she caught me looking and gave me an awkward embarrassed look like she had been caught doing something she shouldn't. I gave her a quizzical look, wondering what was going on, but she shook her head as if it was nothing. I frowned in my confusion and whispered, "Are you ok?" She relented and shrugged apologetically and directed my eyes to where she had been looking.
Suddenly it made some sense. My wife was on all fours picking up the kid's scattered play things with her back to us, seemingly oblivious to the fact that at that angle her tiny denim skirt was covering nothing at all. Not only that, but she had skimpy translucent G-string knickers on that left nothing to the imagination. Everything was so clear that it was even apparent to my sister that my wife was completely shaven. The band of fabric was so narrow that there was more bare skin either side than there was flimsy nylon over her crotch. As she moved about, picking bits of jigsaw up, the tightly stretched piece of fabric was slowly riding up into her pussy. The little fabric that should have covered some of her modesty was so transparent that we had a clear image of her neat pink labia squashed against the gauzy fabric. I almost forgot the situation, I was so engrossed.
I reflected on my sister's reaction and it occurred to me that she should not be too embarrassed; it was not her fault after all. Then it hit me, that was not it; she was embarrassed because I had caught her silently watching my wife for God knows how long, and had seen the affect it was having on her. I looked back at her; I am not much of an actor and the look of dawning realisation on my face was obvious. The idea of my sister being turned on looking at my wife was strangely arousing. I did not know what to say to her, and knowing I could not say anything aloud without embarrassing my wife, I just gave an awkward shrug and whispered "sorry". My sister seemed to relax slightly at my reaction, then gave me a naughty looking smile, and whispered, "It's ok, I was enjoying the view and she is very attractive". Now that really threw me for a loop, and set my mind racing.
For as long as I could remember, I had thought something about my sister was not quite normal. When I was 20 and she was 18, she took quite an interest when I met my first proper girlfriend. She asked me many personal questions about what we did together. As she had not had a boyfriend, yet I initially assumed she was just inquisitive about what happened. We had always been close and shared many secrets. Even so, I was not fully prepared for sharing these types of matters. Eventually my sister's frankness and pleading relaxed my guard. On one occasion, she was getting me to tell her how my girlfriend had her hand inside my pants stroking my cock while I in turn had got my hand inside her knickers and fingered her. Secretly I was getting a bit turned on as I told my sister about it. In my innocence it hadn't occurred to me that my sister might be finding this conversation equally arousing. She even asked me what my girlfriend's knickers were like, and how her pussy felt. Then she had shocked me by telling me in detail what she liked to do to herself with her fingers. At the time, I thought she meant it as advice on how to improve my technique for my girlfriend. However, I was left reeling with such specific knowledge of my sister's sexual feelings, and to go with it I had a mental picture of what she did about them.
Shortly after that conversation, I locked myself in the bathroom and feverishly masturbated to the mental image of my sister playing with herself. That had been the beginning of my very secret, and I thought, sordid fixation over my sister; one that I knew I could never tell another living soul. Through the next couple of years, she would secretly ask me questions about my sex life or even volunteer information about hers. Weirdly, I started to feel torn; I enjoyed hearing my sister's sexual fantasies and activities and talking about mine, but due to the shame of my secret fixation on her, I found it increasingly difficult to have these conversations. I was afraid I would give my secret away so started to tell her less and even discourage her from telling me about hers.
Eventually we had an argument; she started crying saying that we used to be so close but were now drifting apart. I got angry and shouted something about it was not normal for sisters and brothers to talk about this sort of thing, and why did she even want to tell her own brother this stuff. She ran off crying and we never had one of those conversations again. In later years I often noticed her eyeing up girls I brought home but just told myself she was a protective sister looking out for her brother, even though I was the eldest. In recent years, I had occasionally noticed her watching my wife. The fact that my wife often wore provocative clothing led me to tell myself that my sister was probably just taking an interest in a judgemental fashion as women often do, although she seemed to dress in much the same way herself. Now all this took on a different perspective.
As we both looked back at my petite wife's exposed bum, the thought did cross my mind as to how my wife could not be aware of the show she was giving us. Was she really so engrossed in clearing up the lounge? If my sister had not been there, I would have been on my knees behind her in an instant. Instead, we both had to endure the increasing discomfort of our embarrassing knowledge and my ever-tightening trousers. I glanced sideways at my sister, but she was avidly looking at my wife again. I chanced a proper look at her and noticed her erect nipples clearly defined through her tight tee shirt. It was a hot summer's day and she appeared to have no bra on. She looked sidelong at me and caught me eyeing her up. I blushed profusely at being caught eyeing up my own sister. Her reaction surprisingly, was to look me up and down in return.
In the hot summer evening, I had no shirt on at all which made it difficult to disguise the state of my tightening trousers. She seemed to take her time looking at my waist where my low-slung combats revealed the branded waistband of my designer briefs. Due to the ever-tightening situation, I had to shift slightly as I tried to reposition them to allow for my now rigid cock. My sister seemed to take this in for a few moments before returning her stare to my wife's sexy rear view.
