There could be. Fanfiction is all about taking existing characters and creating new scenarios. Given the popularity of both the Harry Potter universe (assuming Harry here is from that) and Superman, it's not a stretch to think that someone has written a story where they are brothers. However, it may not be a very common one as they come from very different fictional worlds originally.
At first, there might be some misunderstandings. Naruto is used to the shinobi world and its ways, while Superman is all about truth, justice, and the American way. But as they spend more time together, they would start to respect each other's strengths. Naruto would admire Superman's raw power, and Superman would be impressed by Naruto's strategic thinking and his ability to come back from tough situations.
One possible plot could be that Harry discovers his true identity as Superman's brother. He might have been separated from Superman at birth for some reason, like a threat to their family. Then, as he grows up in the wizarding world, he starts to show some superhuman abilities which he doesn't understand at first. Eventually, through a series of events, he meets Superman and they realize their connection. Together, they use their combined powers of magic and super - strength to fight a common enemy that threatens both the wizarding world and Metropolis.
One plotline could be that they discover their relation later in life. Harry, having grown up in the wizarding world, and Superman, in his superhero world, suddenly find out they are brothers. They then have to combine their powers and knowledge to face a common enemy that threatens both their worlds, like a powerful dark wizard who has also got hold of some kryptonite - like substance.
It's not a very common or mainstream genre. Harry Potter and Superman belong to two very different fictional universes with their own distinct rules and fanbases. While there may be some niche fanfiction exploring such a wild crossover, it doesn't have the widespread popularity that more traditional within - universe fanfictions do.
Careful Superman and Sweetheart Superman were popular topics in many online novels. For details, please refer to the following examples:
Be Careful Superman and Sweetheart Superman were superheroes in Be Careful Superman and Sweetheart Superman, respectively, created by different authors.
" Be Careful of Superman " was a novel set in the future. It told the story of the main character, Be Careful of Superman. Be careful, Superman has superhuman strength and abilities, but he is introverted and not good at expressing his emotions. In the story, Superman encountered many difficulties and challenges, but he finally became a hero through continuous hard work and courage.
" Sweetheart Superman " was a novel set in the modern world and told the story of the protagonist, Sweetheart Superman. Sweetheart Superman has superhuman intelligence and abilities. She is good at using technological weapons and is an outstanding military commander. In the story, Sweetheart Superman encountered many difficulties and challenges, but she finally solved them through calm thinking and firm determination.
The stories of these two superheroes were very popular, attracting the attention and love of many readers.
Well, one possibility is that Naruto's ninja skills combined with Superman's superpowers would make them an unbeatable duo. Naruto could use his shadow clones to create diversions while Superman uses his strength and flight to take on the main threats. They might also teach each other things, like Naruto showing Superman some stealth techniques and Superman teaching Naruto how to better control his super strength if he had any in this fanfic.
There are countless adventures they could embark on. They could travel to outer space together, with Superman guiding Harry through the vastness of the cosmos. Harry could use his magic to protect them from any strange magical phenomena they might encounter out there. Or they could go on a quest to find a lost artifact that has the power to both enhance magic and Kryptonian powers. Along the way, they would face many challenges. They might have to deal with other superheroes or wizards who are jealous of their combined powers. They would also have to learn to trust each other completely, as their different powers and ways of thinking could sometimes lead to misunderstandings. But through these adventures, their bond as brothers would grow stronger.