Perhaps Naruto's brother could be a long - lost relative from a far - flung part of the ninja world. He could have been separated from Naruto when they were young due to a war or some political intrigue in the ninja clans.
His brother could be an unknown Uzumaki. Since Naruto is from the Uzumaki clan, it would make sense for his brother to be from the same clan. Maybe he was hidden away for some reason, like to protect him from the same threats that Naruto faced as a child.
It could be an unknown brother that was kept secret all this time. Maybe he was hidden away by some enemy of the village and trained to be a powerful adversary for Naruto.
In this kind of fanfiction, Naruto might have an emotional reunion with his brother. Maybe they would exchange stories about their pasts, and his brother could share some family secrets that Naruto never knew.
Another possibility is that he could be the brother of Weiss. Weiss comes from a wealthy and proper family. Naruto's more free - spirited and unorthodox ways would clash with Weiss's upbringing at first, but they could grow to understand and support each other as the story progresses.
In the 'naruto meets his brother fanfic', it's possible that the brother has a different view of the ninja world compared to Naruto. This could lead to some interesting debates between them. The brother might be more cynical or have a darker past that Naruto has to come to terms with. There could also be a rivalry at first, but as they get to know each other better, they form a strong bond. Maybe the brother has some special abilities that Naruto has never seen before, and Naruto is eager to master those abilities as well.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.
The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.
She could be an Uzumaki. Since Naruto is from the Uzumaki clan, it would make sense for his grandmother to be part of this powerful and mysterious clan. Maybe she has some unique abilities related to the Uzumaki's sealing techniques.
He could be a powerful and respected shinobi from the Uzumaki clan. Given the Uzumaki's reputation for strong chakra and unique abilities, Naruto's grandfather might have been a key figure in the clan's history.
It's possible that she is a powerful sage who has been watching over Naruto from afar. She might have sensed his strong chakra since he was a baby and decided to become his godmother in a way. This sage could have all kinds of ancient knowledge and abilities that she could pass on to Naruto.