Yes, there are some out there. You can check fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Naruto is Superboy' and you'll likely find a variety of stories with different takes on the concept.
One common theme is power combination. Since Naruto has his chakra - based powers and Superboy has super - strength, speed, etc., fanfictions often explore how these powers can be combined or used in new ways.
In addition to Naruto and Superboy, there could be other characters from both universes. Maybe some of Naruto's friends like Sasuke or Sakura could be involved. From Superboy's side, perhaps his friends or mentors from the superhero world might make an appearance. They could play important roles in the story, either helping or hindering the relationship between Naruto and Superboy.
In this 'naruto brother of superboy fanfiction', the plot might revolve around them teaming up. Naruto could bring his ninja skills like his shadow clone jutsu, and Superboy his super strength and flight. They could fight against a common enemy that threatens both their worlds, like an evil alien - ninja hybrid villain.
Superboy may have some hidden abilities or powers that he discovers while being kidnapped. These new powers could help him escape. For example, he might find out that he can phase through objects like a ghost. This would allow him to pass through the walls of his prison and get away from Lex Luthor. Another way is that he uses his super - speed to create a distraction and then make his escape while Lex is distracted.
One possible fanfiction could be about Superboy and Artemis teaming up for a secret mission. They might face challenges that test their individual powers and their ability to work together. For example, they could be up against a powerful villain who has the ability to manipulate the environment. Superboy's super strength and Artemis's archery skills would have to be combined in a creative way to defeat the enemy.
The appeal lies in the characters themselves. Superboy's superhuman strength and abilities combined with Wonder Girl's combat skills and Amazonian powers make for a great pairing. Fanfiction writers can create all kinds of stories around them.
One aspect to consider is the character development. Superboy might learn valuable lessons about humanity, love, and family values from the Kents. It could also be a story of acceptance, where the Kents welcome Superboy into their family despite his differences. For example, they could help him control his powers better or understand the human world more deeply.
One great 'Batman and Superboy Fanfiction' is 'The Mentor and the Protégé'. It really delves into the relationship between Batman and Superboy. Batman's brooding nature contrasts well with Superboy's more exuberant personality in this fic.