For Jess the next couple of years was great. She was a happy girl, able to make friends at school, and despite having her knowledge reset she was a smart kid. Sure she wished her father didn't have to work so much, but Joseph was a good father and made time where he could. Of course mommy was always there and the chronivac was always there to smooth out problems.
Jeff on the other hand didn't done quite as well. He didn't really trust his mom after being unborn and left to live 11 years through his sister, and even then whatever that splitting package did removed most of his memories... Well Jeff supposed they really were Jess' memories but still he had a hand in influencing them. He mostly stuck to his room playing games, and wasn't really good at making friends with others his age who he found to be a little immature or uninteresting. At least he played nice with Joseph and Jess though. At first he had been angry but neither really did anything wrong. Jess was simply existing and trying to enjoy her life, but Joseph... I guess he just wanted to have a good life too. It's just he was replacing dad, man of the house, love of mom's life, and the true dad of Jess...
About 5 years after the incident Jess, Jeff, and Jamie all had a copy of the chronivac on their computer or laptops. Then it just so happened that Jamie and Joseph were going out for the night for a date night they had been putting off for half a decade. The siblings were by themselves for about on hour. Jeff on the couch as Jess paced and said "I mean they could just age us older if they wanted to go on a date or something."
Jeff said "That could mess with the timeline a little too much, besides you were never older than what 11?" the 13 year old said dismissively
Jess groaned and said "I mean we could do a non-universe altering age up, Mom could just say she got a babysitter and not-"
Jeff said "And what would happen when both of them get back and the babysitter isn't here." The doorbell rang and Jeff continued "Well that's probably our babysitter. As the elder sibling I'll get it." and then left for the door. Opening the door Jeff saw a guy in jeans, t-shirt, with shaggy blonde hair.
The guy said "Um, hello are you Jeff? I'm Charlie and your mother Jamie hired me to look after you and your little sister Jess right?" Jeff nodded a small spark in a not really existent memory sparking as if he should know who Charlie is... Not like that mattered though right? The two went to the living room where while Jeff only had a small tingling in the back of his skull about who Charlie could be Jess for sure knew. Her memories of her life with Jeff in the back of her skull was fuzzy in some details. Class lectures, and information gained from that was kinda blurry. However people like her only crush her age was crystal clear. Charlie was a lot less clean shaven now that he was in charge of taking care of his own haircuts, but he was the same person she liked... and was now a little less than double her age. The eight year old girl was throwing off love at first sight crush vibes that Charlie was even aware of. Charlie said "Well I'll go get dinner started. I believe your father bought an oven pizza that I just need to throw in. How about we play a game or watch a movie or something while we eat?" As Charlie left Jess felt a strangling sensation at her neck as the collar of her shirt was digging into her throat.
Jeff holding the back of Jess's shirt said "Now then my sister, what are you off to go doing?"
Jess struggling said "Let me go! I need to use the Chronivac ASAP!"
Jeff said "You remember your original life a lot better than I do, why do you need to use the chronivac on that guy?"
Jess somewhat crying said "He's the guy I liked. The one you didn't let me go after... Just let me age to 16 or regress him please."
Jeff said "You know both of those is going to screw with the whole reason he came right?"
Jess said "Let me get older and make him my boyfriend please! You owe me that at least!"
Jeff sighed and got out a chronivac emitter from his back pocket and turned it on and said "Just for the night, then we can ask mom about it... now then how did" Jeff pressed a button and felt himself grow a bit... in all but a single spot which shrank pretty hard. The now busty, wide hipped tween cursed herself for a bad button press. But that gender bender could wait to be restored as Jeff set her sister to 16 years old.
Memories and reality altered a bit Charlie came in after the pizza was starting to get baked and said "Well Pizza's in the oven darling and darlingette." Jeff internally sighed wishing she hadn't pressed the gender button on herself, but for sure the timeline got a little odd. To Jeff's memory her name was now Jenn, and was now for sure Joseph's daughter. Her heart somewhat broke as now Jack wasn't her father anymore, he was just some guy who was now dead probably. For sure Jess and Charlie were a couple, probably thanks to their mother's chronivac DNA.
Later that night in Jess and Jenn's shared bedroom their mother came by and asked "So... I get why Jess used the chronivac to get older. I had expected that. But Jeff why did you-"
"It was a slip of my hands. I was planning on changing back, but Charlie was there and then Dad came home." Jenn biting her tongue for calling Joseph Dad.
Jamie smiled and said "How about you see how well girl you feels. May let you and Jess finally bond your aware selves. Good night."
The two girls flopped onto their beds.
Jenn said "You know we're going to have to age up all your friends right?"
Jess said "Ah... that's going to be a quick problem to fix. Meanwhile I get to be the older sibling now little B-cup."
"Sure little for your swollen mammaries, I like to think I have a decent breast size."
"You know, my first time around I thought it was you making me wish my boobs didn't grow so big... Now It's probably because our mom made our genetics have breasts that are too big." The sisters were actually talking for once, and were actually bonding. Jenn turned back to Jeff more comfortable with having a penis instead of boobs, but the two kept some of the bonding they had and were a lot closer because of it.