Not wanting to raise suspicions by possibly changing Jamie again (assuming its the watch that did it) you decided to test it on another sibling. Christy your 7 year old little sister looked like a good candidate. You walked into the living room to find her playing with her stuffed animals and watching cartoons. She didn't notice you walk in. You pointed your watch towards her and tried to moved the clock forward an hour, however in your anticipation slipped it a lot farther changing the time from 6:00 to 10:00 on accident. You watched on as her body began to stretch rapidly. Unlike her older sister, Christy was short for her age at 3'7, but it didn't look like it would stay that way. She grew taller and taller, soon you could see the beginning of breast buds poke through her shirt which grew out to at least an B cup. "What the heck?" You heard her say. Christy stood up and wobbled a little as she adjusted to her body. She must have been about 11 now, and a whole foot taller. You slipped out of the room before she could see you and heard a little shriek "I've got boobies now... Sissy!" You tucked into another room just as Christy entered the hallway. She ran to Jamie's room where her big sister was looking at her own larger breasts. "Sissy look! I was playing with Mr. Bear when I grew up all of a sudden! Look I have boobies like you now!"
Jamie peered over to her younger sister and immediately went wide eyed. She didn't look quite so little anymore, infact she looked almost like her after her growth spurt expect with really tight clothes. "Holy cow, how did that happen Chris!?"
"I don't know but it sure feels funny... and uncomfortable." She tugged at her shirt which looked like a shrunken crop top now.
"Well of course, we gotta get you out of those clothes, they look like they hurt." Jamie dug through her dresser and pulled out some of her own clothes. "Here these might fit better" She handed Christy the outfit as she shut the door.
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A few hours later your mom came home. As she turned the corner into the living room she saw what looked like Jamie playing with Christy's teddy bear. "Jamie, what are you doing? Where's Christy?" The tired middle aged woman chuckled at her.
"Oh mommy you're home!" Christy hopped up and hugged her tight. "Its me mommy, don't I look pretty? I've got boobs just like you and sissy!"
"What...what is-"
"Its true mom, Christy was just sudden big like this, I grew too! I need some new clothes again." Jamie interjected.
"Oh my god, this is not normal I-" Your mom stood there with her mouth agape at the sight of what looked like to teenage girls before her "Im calling the doctors first thing in the morning. No school for you too tomorrow, obviously we need to buy you new clothes-this is insane." She walked off to her room and shut the door.
"Yaaaay no school tomorrow!" Christy hopped up and down in excitement.
Although you over did it and definitely grew Christy to noticable levels, your horney teenage brain couldn't argue with the results. Something about your younger sisters growing and developing was getting to you. But would you do anything further?