My first fanfic in a little while, I fell badly sick last year with anaemic.

This fanfic was again was largely inspired by a very special friend and RP partner. Big hugs to you!

I like to think if Katsuki had a younger sibling he would be a very loving and doting big brother.

Disclaimer: I don't own my hero academia

The explosive brothers

It was a typical sunny day in the city, people going about their business, pro heroes keeping people safe for the villains and on the way to U.A high was Katsuki Bakugo, heading back to the dorm life after spending the weekend at home. This time though, the ash blonde teen was being accompanied by a much younger ash blonde kid, it was Katsuki's 6-year-old brother Kai, he looked almost a spitting image of his big brother did at that age. As the exploding brothers walked together, Kai had a big smile on his face, he was being allowed to stay at the dorms for a little while with Katsuki and the rest of class 1-A. "I can't wait to be there with you big brother! It's going to be so cool!" Kai burst out in a fit of excitement, holding his arms out, Katsuki looked down at his little brother, a smile appearing over the older boy's face. If there was one people in the world that could make Katsuki really smile and that was Kai. "Just behave yourself ok? I don't want you getting into trouble or anything". Ever since Kai was a baby, Katsuki has been making sure his younger brother does not turn out to be like him, he is always reminding Kai to be kind and respectful to others. "Don't worry Katsuki I will be". The younger brother gave a smile to Katsuki, he knew his big brother was not one to talk, but he was grateful to have a big brother who was always looking out for him. Due to the incident involving Katsuki being kidnapped, it was agreed upon by principal Nezu after Katsuki asking him to have Kai stay at the dorms for a while for his own safety, it was feared that Kai could be kidnapped to and be held to draw Katsuki out to go after Kai if that happened. Kai had been having nightmares for a while even since what happened to his brother, of course he didn't tell no one, but Katsuki could read his brother like a book. He could tell his brother had not been sleeping right and knew he had been having nightmare it was one of the other main reasons Katsuki wanted Kai with him, to make sure his brother slept properly to. Placing a hand on his younger brother's hair, he gently ruffed it grinning. "Katsuki!". Kai pouted out from his hair being ruffled.

The pair soon arrived at U.A and headed to class 1-A's dorm, walking inside with his little brother, Katsuki saw a few of his classmates were already there. "Morning losers!". Izuku who was sitting on the couch smiled at his friend as he saw him walk in. "Morning Kacchan!". Shoto who was sitting next to Izuku saw Kai walk in beside Katsuki, wondering why he had brought a kid with him. "Katsuki, what's with the kid?". The ash blonde teen growled in annoyance. "What's it got to do with you iceyhot? It's my little brother if you must know". Shoto shot a blank look at Katsuki, why did he even bother to ask. Kai saw Izuku and ran over to him. "Izuku!". The younger boy cried out happily as he ran over to him and hugged him. Izuku chuckled and wrapped his arms around the younger boy. "Hey Kai! Nice to see you again pal". Kai knew Izuku the most, due to him hanging out with his brother when they were young, Kai got to know Izuku very well, the green haired teen was the only other person apart from his parents Katsuki trusted the most to look after Kai. Gazing over to Deku, a faint smile appeared over Katsuki's face. "Deku, I need to talk to you later". Hearing Katsuki need to talk to him, Izuku nodded his head. "Sure thing Kacchan". Ochako sitting on the other couch with Mina and Tsuyu all awwwed over Kai. "Aww! You are adorable!". Mina cried out. "Ribbit, you are a cutie". Tsuyu complimented. "I never knew Katsuki had such a adorable little brother!". Ochako said as she smiled over to him. The compliments from the girls caused Kai to blush deep red on his cheeks, causing the young ash blonde as he turned to face the other teens, rubbing a hand through his hair. "Hehe...th...thanks, you are all beautiful though". The comment from Kai caused the girls awws to grow. "He definitely has a different personality from his brother". Mina said in a cheerful tone. "Now that is for sure!". Ochaku agreed, Katsuki of course growled and gritted his teeth, explosions came from his hands."I can be nice and respectful if I want!". Everyone in the room laughed at Katsuki's outburst, even Kai did.

Once Kai had talked with the others, he and Katsuki went up to his brother's dorm room, Izuku had followed to since Katsuki need to talk to him. As Kai was busy sorting out his stuff from his bag in Katsuki's dorm, the older ash blonde talked to Izuku outside. "Listen Deku, you know why I brought Kai here for and you are the other person I trust the most but don't let that go to your head nerd". Katsuk's telling to Izuku how much he trusted him with Kai did mean a lot to him, after all the the pairs relationship had got a lot better recently. "I want you to keep an eye on Kai when I'm not around. He means a lot to me and please don't tell no one else". Understanding, Izuku nodded his head. "Don't you worry Kacchan, Kai will be safe here with us". Izuku remembers Katsuki telling him about Kai's nightmares and him not sleeping well, the green haired teen knew how much Katsuki loved his little brother and would do anything to protect him. After the pair had talked, Izuku went back to his dorm while Katsuki went into his, as he entered, he saw Kai trying to pick up and put on one of his gauntlets. The sight made Katsuki chuckle a little, his little brother wanted to be hero when he was older, plus he had the same quirk as Katsuki. "They are a bit too heavy for you to handle pal. I'll go and see that crazy invention girl to see if she could make some for you, of course they will be smaller and ones you can pick up". Katsuki told him as he sat on the edge of the bed. Putting down the Gauntlet he was trying to pick up, Kai gave a wide smile at hearing his brother was going to get some made for him. "That will be so cool big brother!". Walking over to the bed, Kai climbed on and sat next to the older teen and laid his head on Katsuki's right arm, holding onto it to as he closed his eyes. Looking down at Kai, Katsuki gave a genuine smile. "You will be safe here pal, I promise you that". The tone of Katsuki's words were genuine, plus it was a promise he made to him when Kai was born. "Thank you Katsuki". Kai replied in a soft tone, knowing he was safe made him feel more better and the fact he still had his loving and doting big brother around.

Now I just may continue this for a couple of chapters, but it depends on the feedback and reviews I get.

Thanks for reading and remember go beyond, plus ultra!