You're the older sister of the Batboys and somehow you were transformed into a 3 year old girl.
Your age:23
Dick's age:22
Jason's age:19
Tim's age:16
Damian's age:13
3rd person view
"RICHARD JOHN GRAYSON WAYNE, JASON PETER TODD WAYNE, TIMOTHY JACKSON DRAKE WAYNE, AND DAMIAN AL GHUL WAYNE, GET DOWN HERE THIS INSTANT!" Bruce yelled, the four boys looked at each other in fear and headed downstairs.
The four boys saw their foster father/father holding a 3 year old girl in his arms, "seriously, Bruce? Another one?" Jason asked "shut up, Jason," said Bruce "now, who turned Y/n into a toddler?" the four brothers stared at the toddler, "THAT'S Y/N?!" the four chorused "yes this is Y/n," said Bruce "now, answer my question," "we didn't do it," said Dick "yeah, we will never do that," said Jason "we're not that stupid," said Tim "why would I turn my older sister younger?" Damian replied "I know the girls aren't that irresponsible and if none of you did it then it must've happened during patrol," said Bruce, he placed Y/n on the floor and watched her crawl to Damian, "I'll be looking for a cure in the Batcave, meanwhile, watch Y/n," said Bruce and he left. Once he left, Dick, Jason, Tim and Damian just watched Y/n crawl over to Damian, Damian then picked her up, "so what do we do?" asked Tim "see if Y/n knows who we are," Dick said, he took Y/n from Damian, "hey Y/n, you know me?" Dick asked "Duckie!" Y/n said, Jason and Tim burst out laughing while Dick looked slightly offended, "Duckie!" said Y/n again, Jason took Y/n from the eldest brother, "hey, n/n," he said "do you know me?" "JJ!" Y/n said "close enough," said Jason, Tim stole Y/n, "how about me?" Tim asked "Timmy!" said Y/n "dang it!" said Jason and Dick, Damian snatched Y/n from Tim and held her in his arms, "obviously she knows who I am since I'm her blood brother," said Damian, Y/n placed a hand on Damian's nose and said "Dami," "it's normal for her to call you that," said Tim "true," said Dick.
Few hours later, they lost Y/n.
"Grayson! did you find her?!" Damian asked "no! did you?!" Dick replied "why would you ask me that if I'm asking you?!" "point taken," Jason and Tim running in with Y/n, she tried to squirm out of Jason's grip and bonds that held her.
"Todd! why is my little sister tied up!?" "because she ran off more times than we can count!" Jason snapped, Y/n continued squirming around, "JJ, let go!" Y/n said, Damian pulled her into his arms and made her face him, "stop. it," he said "let go!" Y/n said, Damian sighed and untied her, "now, if you run away again, we will not untie you until Father finds a cure," Damian warned "understand?" "yes," Y/n said, Damian got up and took Y/n's hand, both headed to the main living room with their brothers following them.
*time skip*
When Bruce returned from making the cure, he found his children all sprawled together on the couch. He carefully took Y/n from Damian and carried her down to the Batcave, Damian instantly woke up and bolted after his father, Jason, Tim and Dick felt Damian taking off making them wake up, they all chased after him.
The 4 boys saw their 23 year old sister back to her old self, Damian happily hugged her, "hey, Dami, thanks for taking care of me," she said running her fingers through Damian's hair, one by one, her younger siblings welcomed her back, "to be honest guys? I don't really remember what happened when I was a toddler," said Y/n with a shrug, the 4 brothers launched into the story making Bruce shake with silent laughter.