Well, sometimes in fanfiction, his brother might be a mortal who discovers his demigod heritage later. This could add an interesting twist to the story as he has to adapt to the world of gods and monsters. Or it could be a long - lost half - brother from a different camp, like a son of Poseidon from another part of the world who was hidden away for some reason.
There's a fanfiction called 'Brotherhood in Camp Half - Blood'. In this story, Percy's new brother is introduced in a very dramatic way. The author does a great job of showing how the brother fits into the world of Percy Jackson, with lots of action and adventure sequences. It also explores the relationship between the two brothers in depth, like how they deal with the challenges together and support each other in the face of danger.
In many fanfictions where Percy Jackson is Nico's brother, it creates a whole new dynamic in the story. It often leads to different interactions with other characters. For example, their relationship with Annabeth might change. Percy could be more protective of Nico, and Nico might feel more secure having Percy as a brother. It also gives room for exploring their family history in new ways, like how they deal with their demigod powers together and support each other in the face of various challenges in the demigod world.
Some of the gods might also be important characters. Poseidon, Percy's father, could have an interesting reaction to Percy's new relationship. Hades, as the god of the underworld where Styx is located, might also be involved, either as an ally or an obstacle depending on the direction of the fanfiction.
Some Percy Jackson fan communities on social media platforms like Reddit or Tumblr might also have links or discussions about 'Percy Jackson Brother Fanfiction'. Sometimes fans will share their own works or recommend good ones they've read.
Well, it could be about Percy discovering he has this unexpected connection to Ares. And then he has to deal with the reactions of his friends like Annabeth. Some of them might be distrustful of this new relation. Percy would then try to find out more about his connection to Ares through exploring old prophecies and ancient sites, all while trying to keep his regular demigod duties in check.
Well, one possible plot could be Percy and Zoe having to team up against a common enemy. Maybe a new powerful monster emerges that neither of them can defeat alone. So, they have to put aside their differences (if any) and combine their skills. Percy with his water powers and Zoe's archery skills would make a great team. They could start out not trusting each other much, but as the story progresses, they learn to rely on one another and form a strong bond.
Well, one possible plot could be Percy discovering he's Zeus' brother in a very unexpected way. Maybe through some ancient prophecy that was long forgotten. He'd then have to deal with the power struggles within the Olympian family, as well as his own identity crisis. Another aspect could be his relationships with other demigods changing, as being related to Zeus is a huge deal.
Well, one possible plot could be Percy having to hide his relation to Kronos while still fighting against the Titans. He might struggle with the internal conflict of having a connection to such an evil entity as Kronos while trying to protect his friends at Camp Half - Blood.
A third common theme is adventure. Since Percy is part of the Hunt, he goes on various quests and adventures. These adventures usually involve mythological creatures and places. The fanfictions describe his experiences in these new and exciting settings, and how he uses his powers and the skills he learns from the Hunt to overcome challenges.