Kyon is often a popular character. He has his own unique personality and his interactions with Haruhi and potentially her little brother can add a lot of interesting dynamics to the story. Another could be Mikuru, as she is cute and kind - hearted, and her reactions to the little brother's presence or actions can be quite endearing. Yuki might also be a prominent character, especially if there are some mysterious elements in the fanfiction that she can be involved in, like if the little brother stumbles upon some of her secrets.
Well, Koizumi is a character that often shows up in these fanfictions. His cool and collected demeanor can contrast well with the little brother's possible naivete or energy. He might be the one to guide the little brother in understanding some of the more complex aspects of Haruhi's world. Also, Tsuruya - san is quite popular. She has a big personality and her friendship with Haruhi could extend to include the little brother. She might be the one to give the little brother some valuable advice or get him into some fun and crazy adventures with Haruhi.
Well, in some haruhi has a little brother fanfiction, the little brother could be the one who discovers a mystery that Haruhi and her friends are oblivious to. He then has to convince them that there is something strange going on. It could also be that the little brother has a different view of the world compared to Haruhi, and through their interactions, Haruhi starts to see things from a new perspective. Maybe he's really into music and introduces Haruhi to a whole new genre that she ends up loving and incorporating into the club's activities.
Kyon could be a great addition. He often has an interesting perspective on Haruhi's antics and his interactions with both Haruhi and Mikuru could add depth to the story. Also, Yuki could be included. Her stoic nature contrasts with Haruhi's exuberance and Mikuru's more timid personality, creating some interesting dynamics.
Denmark could be one of the main characters. He is often shown as Norway's friend/rival in the Hetalia series. He might come around to check out the new little brother and end up getting involved in their daily lives, maybe trying to show the little brother his own Danish culture, like Lego and Danish pastries.
Well, they could be very protective of each other. Hermione, being the intelligent and strong - willed witch she is, might take it upon herself to teach her little brother all she knows about magic. And her little brother could look up to her and be her biggest supporter in Hogwarts, always cheering her on during her academic achievements and adventures.
It might also be a term of endearment for a younger male friend or acquaintance. In some groups, people use 'brother' in a friendly way, and 'little brother' could be a specific person within that group who is no longer interested in stories.
There's not enough information to say exactly who the little brother is. He could be an ordinary boy in a family who is the youngest among his siblings.
At first, it might be a bit awkward. Since they likely grew up apart or in different situations. But as they spend more time together, they'd start to understand each other better. They could share their problems, like Haruhi talking about her financial struggles and Harry sharing his experiences with the wizarding world's challenges.
Obviously, Neji himself would be a very important character. His actions and words would have a great influence on his little brother. Also, other members of their clan could be main characters, like their parents or other relatives who play roles in the little brother's life and ninja training.
The big brother and the little brother are the main characters. The big brother could be a confident and responsible character, while the little brother might be more naive and in need of guidance. There could also be friends of the brothers in the story that interact with them, but the focus remains on the relationship between the two brothers.
Well, the plot could revolve around family secrets. Maybe Harry discovers that their family has some sort of special heritage that ties into both the world he comes from and Haruhi's world. They could go on a journey together to uncover the truth about their family, all while Haruhi is still dealing with her school life and the Host Club. Harry might have to protect Haruhi from some threats that are related to this family secret.