Well, you could write a fanfiction where Naruto discovers a long - lost relative who has a very different view on the ninja world. This could create a lot of internal conflict for Naruto as he tries to balance his own beliefs with those of his newfound family member. Another idea is to set the story in a parallel universe where the roles of the characters are reversed. For instance, the Akatsuki are the good guys trying to protect the world from an evil Hidden Leaf Village. And a third option is to have Naruto accidentally end up in a world without ninjas and has to figure out how to get back while also learning about this new world's way of life.
A great plot idea could be centered around a new, powerful enemy that only Naruto's son (or a new generation character) can defeat, with Naruto having to train and guide him. This would show the passing of the torch. Or, you could do a story where all the characters lose their chakra powers and have to rely on their wits and physical skills. It would be an interesting twist on the usual ninja battles. Also, a story about a hidden clan within the Leaf Village that has a special power which Naruto and his friends have to discover and protect from an outside threat.
One idea could be a time - travel plot. Your brother's favorite character from Naruto, say Naruto himself, travels back in time to prevent a great tragedy that was about to befall the Hidden Leaf Village. Another plot could be a 'what - if' scenario. For example, what if Sasuke never left the village? You could explore how the relationships between the characters would develop differently. A third idea might be a crossover plot, like Naruto characters meeting characters from another anime world, but still keeping the essence of Naruto's universe intact.
Perhaps Naruto's half - brother was raised in a different village by an enemy of Konoha. He initially hates Naruto but as he gets to know the real Naruto and the values of Konoha, he has a change of heart. They could team up to stop a conspiracy that threatens both their villages. He might also have some special skills in espionage which he uses to their advantage.
Well, a possible plot might involve Naruto and Meliodas growing up together in a world that is a mix of the Naruto and Seven Deadly Sins universes. They could face discrimination because of their unique powers and brotherly bond. Or perhaps they are separated at a young age and have to find each other again while uncovering secrets about their family and the two worlds. It could also be that they have to protect their family's legacy which is tied to both the ninja and demon - related aspects of their respective worlds.
Well, a cool plot for 'Naruto and His Twin Brother Fanfiction' might be that the twin brother has a special ability to communicate with animals, just like Naruto can with the toads. They could go on adventures together, with the twin's animal friends helping them out in battles. Maybe the twin brother also has a secret connection to a powerful clan that Naruto doesn't know about, which could add a whole new layer of mystery and drama to the story.
One idea could be Naruto suddenly finding himself in a world similar to 'My Hero Academia' and having to adapt to their different power systems. He might start teaching his ninja skills to the students there, creating a whole new dynamic.
Another plot idea is that the baby is from a future time where Naruto's world has changed. The baby has come back in time to prevent a great disaster that will happen in the future. This would involve the baby trying to convey important messages to Naruto and his allies, but in a way that they can understand given the baby's limited communication skills.
A plot could revolve around Kazehana teaching Naruto about her world's special form of chakra control. Since Naruto has always been eager to learn new ways to improve his skills, this could be an interesting story. He could then use this new knowledge in his own world to fight stronger opponents. For example, Kazehana might show him how to use wind chakra in a more refined and less energy - consuming way.
A more complex plot idea could be that there is a prophecy about Naruto and Raven. As Naruto is the little brother, he is initially seen as the weaker one, but as the story progresses, he shows that he has unique qualities that are essential to fulfilling the prophecy. Along the way, they face many enemies who want to stop them from achieving the prophecy's goal. Their relationship evolves from a simple brother - sister bond to a powerful partnership that can change their world.
One idea could be that they discover their relation after a long time. For example, Naruto has always felt a special bond with Sakura, and when they find out they're siblings, it adds a whole new layer to their relationship. Naruto might be more protective of Sakura in a different way than before.
One idea could be that Sunset Shimmer's little brother is a new student at Canterlot High. He could struggle to fit in at first because of his sister's reputation, but then find his own group of friends through his unique talent, like being an amazing artist. Another plot could involve him getting caught up in a magical mystery where he has to use his wits to solve it and prove himself to his sister.
Well, a great plot idea could be that the little boy is actually from a long - lost clan in the Naruto universe. His family was wiped out, but he has a special mark on his body that holds the key to a great power. As he tries to figure out his past, he meets different characters from the Naruto series who either help or hinder him. He could also be a natural at a particular type of ninjutsu that was thought to be extinct, like some form of water - based illusion ninjutsu.