Okay so let's just clear this up, you and Hiro are 2 or so and everyone else is 18 or 19 so in other words, this is an alternate universe story!
I received some inspiration from SavannaSawyer so I want to thank you for that!
3rd person P.O.V
Hiro was a baby. And like most babies, curiosity got the best of him. His older brother Tadashi just didn't know how to handle the kid.
"Hiro, stop sitting on Mochi!"
"Hiro, take that food out of your nose!"
"Give me my hat back!"
"Don't break that!" It was a constant cat and mouse chase for the older Hamada.
Nothing and no one could stop Hiro Hamada, he was just to cheeky. Not even Fred or Honey Lemon of GoGo or Wasabi could stop him.
"Hiro eat your food." Tadashi said as the gang tried to get Hiro to eat. Currently nothing was working.
"Okay daddy." Hiro said which caught everyone off guard.
"Hiro... Called you daddy... Maybe the problem isn't him being mischievous... Maybe he just needs a friend?" Honey Lemon suggested.
Hiro lifted his head at those words, crawling to Honey Lemon and nuzzling her leg. "Too adorable!" She squealed, picking him up and cradling him.
"Maybe the little guy needs someone his own age." Fred suggested.
"But that will be hard to find someone like him, other kids disregard him because of his intelligence." Wasabi pointed out.
The gang had hit a brick wall, Hiro had no friends due to his complex brain, creating things other kids called "weird". While others were being read story books, he began reading chapter books on his own.
"I have an idea." GoGo piped up.
"What?" Tadashi asked as Honey Lemon put Hiro back on the floor.
"I know someone who the kiddo can play with, he will like them." GoGo said.
"Who?" Wasabi asked.
"I'll show you tomorrow, it's a surprise." GoGo said.
"Well that's a first." Fred said. The gang continued to play with Hiro until it was his nap time, that's when the gang bid their goodbyes to Tadashi and Honey Lemon kissed Hiro's head softly, before leaving the cafe.
Tadashi smirked at his sleeping brother, what was he going to do with him?
The next day, GoGo had come around extra early with a bundle in her arms. "Hey GoGo!" Tadashi cheered. GoGo quickly put a finger over her lips as a wailing sound could be head.
"Great, woke her up."GoGo dead planned. GoGo rocked the baby in her arms until it stopped crying, curiosity got ahold of Tadashi who tried peeking.
"Go get Hiro, the others are on their way." GoGo said. Tadashi did as told and sure enough, by the time he and Hiro had crawled down the stairs, everyone was waiting.
"Hiro, I want you to meet someone." GoGo said who was now putting another baby on the floor.
"Hiro, this is (y/n), my baby sister, (y/n) this is Hiro, my friend's baby brother." GoGo said, letting (y/n) crawl to Hiro with interest.
They bumped each other's head and (y/n)'s eyes began to swell with tears. "I'm sowwy." Hiro said, crawling closer to (y/n) and kissing her head better.
"AWWWW!" Everyone squealed including GoGo.
"It's okay." (Y/n) smiled.
"I am Hiwo." Hiro said.
"I'm (y/n)." (Y/n) said. Hiro led (y/n) up to the brothers bedroom where they crawled up the stairs. The gang followed with great interest, only to be met with a shocking sight.
Hiro and (y/n) both sat in Tadashi's desk chair, playing on his laptop. "Well there's something you don't see every day." Wasabi whispered.
(Y/n) and Hiro crawled off the chair and began to crawl over Tadashi's bed.
"Hey! Your gonna ruin the bed! Oh and I just fixed it!" Tadashi groaned. The babies only giggled and continuously tried to mess it up more.
When lunch time came around, both babies refused to eat at the table. GoGo sighed and placed the sandwiches on the floor as they both grabbed one each.
Hiro placed the sandwich in front of (y/n)'s mouth who took a bite. (Y/n) did the same and the gang watched as the two fed each other.
Once they were done, they began yawning and rubbing their eyes. Tadashi scooped them up and placed both babies in Hiro's crib.
They rolled around and eventually snuggled together for warmth. When the gang tried to pry them apart however, they always rolled back together.
"They are just to cute! I can tell they will be two peas in a pod when they're older." Honey Lemon fangirled.
"I know right?!" Fred agreed.
(Y/n) and Hiro didn't hear anything though, they were asleep, in each others arms.