Jeff looked up conjoined twins and soon realized it meant he would become an identical twin sharing the same genes with someone. The Merging package which also caught his eye would allow him and the other person to keep their independent identity, but this will turn him into a genetic copy of someone else or them into a copy of him.
Jeff pondered, considering action movie stars and billionaires but he would rather be them, not be conjoined to them... For now, for fun, Jeff decided he wanted to try being conjoined with his father. In addition to copying both his and his fathers profiles for safe keeping, he immediately put in protections so that he could painlessly will himself to separate or reconjoin as he desired within seconds. Nobody would find his or his dad's conjoinment or disjoinment weird or unusual, even if caught in the middle of the switching. Jeff took special care to ensure reality would change so that things would always seem normal as far as anyone is concerned regardless of if he is conjoined or not.
Finally, Jeff didn't want to loose his identity right away... Although he would be aware of his original reality as well as whatever reality currently was, based on if he was conjoined or not, his physical attributes would only change 5% an hour while conjoined, this would give him at least 20 hours to ease into becoming his father's identical twin.
Though Jeff was eager to try this... it was scary to click the submit button. "What if I forgot something or didn't take something into account?" the nagging voice in the back of his head asked... "Then I can just disconnect and try again..." he said bravely dismissing the concern and with that he clicked submit.
A popup immediately appeared offering for him to continue or cancel, "You have made modifications to a basic package, this package will begin by conjoining you to your target of choice. The modifications you have made will then become effective and available." Jeff clicked continue before the nagging voice could chime in...
On the screen, Jeff's profile popped up, it showed all his stats and he saw the text under familial relationships change. His father moved to the brother position and his grandparents took his parents position. "Woah" Jeff muttered. It made sense but he hadn't thought it through. His siblings became nieces and nephews and his mother switched to Sister-in-law but that was the extent of changes to his profile that he saw.
A strange tingling in his brain occurred and suddenly the world where Jeff was being raised by his brother suddenly made sense. He was obviously an accident (a miracle given his parent's ages) and by the time Jeff was 7, his parents were slowing down. Mike stepped up and slowly took over raising Jeff, eventually letting Jeff live with him and treating him like a child of his own. This allowed his parents to focus on retirement preparation rather than school field trips, child oriented vacations, and helping with homework each night.
Jeff waited for something else to happen, "I guess this is the basis for the new reality while Mike and I are separated, but I thought..." Jeff's profile flashed on the screen and Mike's popped up too. Many of Jeff's stats suddenly became disabled and in the input boxes it simply listed "Conjoined with Michael". Jeff's age was now listed as 42 to match his dad's age and his former siblings showed up as Jeff and Mike's children instead of just his brother's children additionally his former mom was now his wife as well as Mike's.
Jeff's clothes vanished and alarm ensued as Jeff feared he would loose his identity immediately after all. Jeff ran to his full body mirror and watched as he grew taller and his muscle began filling out. It was clear his body wasn't just growing taller as his naked body easily showed his package thicken and grow, a moment later body hair quickly erupted everywhere. As the changes continued, weight continued to materialize but it was no longer the lean muscle of a young man just out of his teens.
Jeff's body was no longer that of a 16 year old but his neck and head was. There was a noticeable difference in skin texture and color and despite how comical it was to see his head placed upon his father's body, similar to a bad photoshop job, the body, its feelings, and perspective all felt pretty normal. Jeff looked closely at his new body and noticed that the graying process was running rampant through his new body hair and he vaguely recalled it starting to become obvious in his mid thirties.
"Huh..." Jeff muttered enjoying the disparity between how weird the situation was but how normal it felt. "I wonder what's next." His voice
hadn't undergone any change whatsoever and seemed out of place on his middle aged body... from the perspective of 16 year old Jeff... from his 42 year old perspective everything was normal.
Across the room, the Chronivac began the next phase of the process and downstairs Mike had a sudden need to check on Jeff. Within a few seconds Mike was climbing the stair making his way to where he knew Jeff was. Similarly, Jeff had a deeply rooted desire to see his Brother, err, Father? No Brother... Though it wasn't for any reason in particular, it just felt weird to have not seen him recently.
Mike knocked on the door and announced himself, without thinking or even realizing he was naked, Jeff opened the door and asked him to come inside. The two smiled and embraced in a hug and as they squeezed one another, Jeff's body slowly melded into Mike's as though he was becoming ethereal. Jeff turned around, passing through Mike's body as though it wasn't there and the pair aligned their bodies instinctively.
Their bodies snapped into place and were no longer two, their body was suddenly shared. Reality again warped and heaved as Jeff's former bedroom became a spare office. Mike and Jeff's shirts changed to accommodate two heads but beyond that, things went on with minimal changes.
Though Jeff still looked like himself from the neck up (currently) he was treated and even thought of himself as a 42 year old who had been conjoined all his life, if he tried to remember things, a whole set of memories associated with this new existence were available to him. Memories of dating, sex, becoming and being a parent, work, friends, parties, driving, and everything else tied to being a middle aged man came to him like normal with the added benefit of sharing each experience with his brother...