Jeff's sight slowly returned and he tried to work out where he was. Looking around, he saw a dresser, with bottles of perfume and makeup on top. There was a hairdryer lying carelessly on the floor, next to some scattered clothes.
"Well, at least I seem to be in some woman's room" he thought.
He took another look and recognised the posters hanging on one of the walls. They belonged to his sister, meaning he was in her room. He guessed that, from the angle he could see, he must be sitting on her bed. Jeff felt a slight pang of annoyance. Apparently the Chronivac didn't function correctly, it just moved him from sitting in his chair, to sitting here.
Someone spoke just behind him. "Hurry up, before they get back!"
Startled by the voice, Jeff tried to stand up, but found himself unable to move. He thought he recognised the voice, then suddenly felt sick. It was his sister. In his haste to try out the Chronivac, he neglected to fully read the options. It had selected the closest viable target to transform him in to, which happened to be his sister, Nicole, in the room next to his. He felt his head (or mind) spinning; he could not believe he was his sister's vagina. The idea of being so intimately close to a woman was, in theory, quite exciting, but he never planned it to be his sister. He was wholly disgusted. He could feel a dampness on his lips. Wait, not his lips but hers, her labia. He could taste and smell the liquid oozing out. It had a sweet, almost enjoyable taste and fragrance, which only added to the disgust he felt.
What he was seeing now made sense, she must be on her bed, with her rear pointing up on display to whoever she was talking to.
His mind was racing. Who could she be speaking to? She never mention having a boyfriend (or girlfriend), or even brought anyone home.
Jeff wanted to get out of here. His perverse excitement about the situation had been replaced with disgust and revulsion. He did not want any part of this, not with his sister.
"Don't worry, they'll not be back for ages yet" a voice replied from outside the room. Jeff's blood ran cold, as he recognised the voice as belonging to James, his brother!
One of the options selected, that Jeff had not payed full attention to, was that of "reality adjustment". He reasoned that people may become worried if he was missing, so opted to have people not notice. He assumed it would simply put him out of people's minds until he returned, but what it did was altogether more complete. It had spawned a separate timeline, one where he was never born. He had not existed as a person. This meant that he had not lived here, he did not spend most days on the computer or playing games. He was not there when his brother and sister were alone, while their parents were at work. Without another person about, his siblings would play together and grow closer, closer than they should have. In this timeline, Jeff wasn't there, sitting between them on the sofa. When they both turned to speak, their lips met and they accidentally kissed. This sparked something and they became more and more involved.
Jeff knew none of this. All he knew was that he did not want to be here.
The door opened, and James walked in. He was naturally muscular, but his fit lifestyle added to his physique. He has probably finished a run or a game of football, before coming home and stripping off. The sweat on his body reflected the light, making him glisten. He said something to Nicole but Jeff wasn't listening. He saw the length and girth of James' dick and felt shocked and somewhat scared.
James had a massive member, which stood erect. It would stretch and deform Nicole's pussy and Jeff started to panic at the thought. He did not want to be penetrated by his brother's cock, especially not one of that size.
The head of the cock hovered in front of Jeff. This close, he could smell the sweat and musky odour drifting from his brother; a fresh wave of revulsion overcame him. James proceeded to gently massage the entrance to Nicole's vagina, and she made an appreciative sound. To Jeff's horror, he could taste the mingled flavours of sweat and precum. The salty, masculine goo was rubbed against Nicole's pussy and Jeff's mouth. Jeff would have vomited if he could, but instead felt himself become wetter.
The head pushed against her hole, Jeff feeling uncomfortable as his mouth is forcibly expanded. As the pressure increases, it starts to hurt.
"oh god no, please stop" Jeff tried to yell, but was unheard.
Suddenly, James' member surges forward, the combined force and lubrication overcoming the strain. Nicole lets out a moan of pleasure as James enters her properly, but Jeff screams silently.
"I- it feels like it's in my mouth. It's forcing my mouth open" he thinks.
James begins to thrust gently, back and toward. They've done this countless times together and he knows how to please Nicole. He places one hand on her waist, reaching the other around to massage her breast. Jeff feels another stab of pain as the cock enters deeper, further stretching him. Nicole seems to not feel the pain, but instead feels pleasure. Her cheeks have become flushed and she asks James to increase his speed. Jeff is filled and emptied faster and faster, each thrust painfully stretching what feels like his throat. Jeff hopes this is over soon, but his siblings have had a lot of practice and James has a high stamina, meaning they can be at it for a long time.
It feels like hours have past. The pain for Jeff seems to have dulled, but it was replaced by a strange queasy sensation, and a mix of disgust and pleasure. Being physically connected to Nicole means Jeff is reacting to the sensations and the hormones pumping through her blood. James' cock is thrusting in and out rapidly and roughly, his balls bouncing against Nicole's clitoris. The sensation both revolts and arouses Jeff, which further revolts him. James grunts suddenly, and speeds up, causing Nicole to moan loudly in ecstasy. A large jet of cum shoots out of James' cock, followed by several more. Jeff's mouth is filled with a thick, slimey liquid. The disgusting salty and strong smell cum tastes strangely enjoyable to Jeff. Nicole's orgasming body causes an involuntary reaction in Jeff, causing him to feel great pleasure.
They collapse on the bed, with James' cock still inside Nicole as they spoon and cuddle lovingly.
-----
Over the next weeks, months and so on, James and Nicole continued to show their love and have sex, unaware of Jeff. Jeff should have returned to normal after several days, but due to the diverging timelines, there was no 'Jeff' to restore, nor was there a Chronivac owned by Jeff to do the restoration. Jeff continued to live as his sister's vagina. Although he resisted the feelings, he eventually came to like and even love the stimulation from his siblings. Overtime his mind faded and he only existed to feel pleasure.