I originally wrote this as part of a longer multi-chapter story which is yet to be completed. It will still feature in that story in due course but for those who like short stories, it works perfectly well as a complete tale in its own right.
It's difficult to know to which category this story belongs. It's hardly incest in the strict sense of the word, though some might regard it so. In the ends I opted for Loving Wives - which I suppose Rachel must be.
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Rachel and Helen were two beautiful identical twins in their early 20s. Both were highly desirable so it comes as something of a surprise to most people that Rachel is married but not Helen. To be honest, most men would have great difficulty deciding between them and would probably settle for trying to fuck them both, preferably at the same time, but that's men's fantasies for you. But not Simon, though. He picked Rachel and married her.
This story comes about because Helen had been adamant for a long time that no-one could tell them apart. Rachel was fed up with hearing her twin make this claim so she decided to bet Helen £100 that Simon would be able to spot the difference. She proposed that one evening Helen should take her place and be at home when Simon returned home from work. The terms of the bet were that she had to cook an evening meal for them and spend both evening and night together, without Simon realising she wasn't Rachel.
Helen was outraged that her sister should suggest such a thing - though Rachel was quite aware that Helen secretly fancied Simon and if she hadn't married Simon, Helen would probably have grabbed him. Rachel reassured Helen that she didn't need to fuck Simon. She could always say that her period had started, giving her an excuse to keep her panties on in bed. Simon had already seen Helen topless on the beach, so he would hardly be seeing anything new. All she had to do to win her £100 was to maintain the pretence until midday the next day.
Helen wasn't well off so £100 seemed like a lot of money for what she assumed would be a certainty. Of course, what she didn't realise was that the whole thing had been set up and Simon knew what was happening. Rachel and Simon realised that if Simon made a full-on sexual approach to Helen he was likely to be rebuffed, regardless of the £100, but if he took it step by small step, to protest about any individual small step would not seem worth risking £100 for. Simon likened this to boiling frogs. A frog dropped into a pan of boiling water would leap out immediately and would survive but if you put the frog in a pan of cold water and gradually heated the water to boiling, the frog would be doomed.
When Simon arrived back at their flat on the appointed evening, Helen was already busy preparing dinner. His first small step was to kiss Helen's neck and nuzzle her ear lobes as she worked in the kitchen. Helen had no problem with this; indeed, it was obvious that she quite enjoyed it. After he had changed out of his work suit, Simon poured them both a drink. While passing Helen her drink, he took the opportunity to run his hand over her behind, finishing with a playful slap. Helen took that in her stride too.
A while later, Simon came up behind Helen and put his arms around her, before sliding his hands under her blouse and cupping her naked breasts and rubbing her nipples - both sisters were fairly small-breasted and didn't wear bras. Helen was torn about this. She enjoyed the physical sensations but was unsure where it was leading. However, £100 was £100, so she merely pointed out that she was working at a hot stove and needed to concentrate.
Simon's next small step came after dinner. The two of them were standing up in the kitchen after clearing the table. Simon took Helen in his arms, thanked her for a truly delicious meal, and kissed her deeply on the mouth. As he was doing this, he ran his hand over her behind once more.
'Oh', he said, with a well-rehearsed note of surprise in his voice, 'you promised me that you weren't going to wear panties this evening.'
Of a sudden, Helen realised that Rachel had set her up so that she would lose the bet and she was furious with her sister. It was also clear that if Rachel had made such a promise only the previous day, the 'I'm on my period' excuse wasn't going to hold water. The combination of anger with her twin and a renewed determination to win the bet fired her up, as Rachel had known it would.
'I got too tied up with preparing the meal', she said, reaching under her skirt and pulling down her panties. 'There', she said, 'a promise is a promise and I always keep a promise', letting the panties fall to the floor and stepping out of them.
Helen's mind was now working overtime. The situation was beginning to get a bit out of hand and could only go in one direction. On the other hand, she was quite enjoying the way it was going and she could feel the moistness staring to develop between her legs. It also felt good to get one back on her scheming twin.
Simon and Helen settled down on the sofa to watch some TV. Simon put his arm around his sister-in-law's shoulders and rested his hand on her breast. He was careful to act casually, doing something that might come naturally with the woman who was supposedly his beautiful young wife. Beyond that he didn't push it too far. His next opportunity came, though, when the late evening film began, a film renowned for its sexual theme and very explicit scenes. It wasn't long before it started to have an effect.
