In such a fanfiction, the plot could involve the brother having memories of a past life. This would lead to him guiding Harry in ways that Dumbledore or others couldn't. Maybe they'd explore new areas of the wizarding world that were previously unknown, all while trying to keep their relationship a secret from Voldemort and his followers. Their bond could be a key factor in the ultimate battle between good and evil in the wizarding world.
One possible plot could be that the reborn brother has a different view on the wizarding world's politics. He might try to convince Harry to take a more active role in changing the way things are run. Along the way, they could encounter ancient magic that has been long forgotten. Their relationship would be tested as they face different challenges, like dealing with the Ministry of Magic's interference, and also dealing with their own personal growth. The brother's presence could also change the relationships Harry has with his friends, as they all adjust to this new addition to their group.
Well, it could be that Harry, as James' brother, discovers that there were more secrets about his first life than he thought. Maybe he finds out that there was a hidden power within him that was never fully awakened in his previous life. This new discovery could change the way he approaches magic and his role in the fight against the Dark Arts, and it might also lead to a different ending to the battle against Voldemort.
In this fanfiction scenario, Harry Potter might change in several ways. His perspective on life and death could shift. Knowing that his brother has some sort of'reborn' aspect could make him question the finality of death more. He could also become more empathetic towards those who have lost loved ones. Emotionally, he might be more stable as he has a family connection now. This new bond could also make him more willing to take risks in the name of protecting his brother, which is a different kind of motivation compared to just fighting Voldemort for the sake of the wizarding world. Additionally, he may develop new magical abilities or skills as a result of the influence of his brother's unique situation.
The protective brother can change the plot significantly. For instance, if he's highly skilled in magic, he can prevent Harry from getting into some of the dangerous situations he faces in the original series. He might be able to stop Harry from entering the Triwizard Tournament by interfering with the Goblet of Fire's magic. This would then change the entire course of that year at Hogwarts and Harry's relationship with Cedric Diggory and others.
One possible plot is that their brotherhood is a secret that has been hidden for a long time. As they find out, they have to deal with the implications in both the wizarding world and Chuck's world. For example, there could be a prophecy related to their union that puts them in danger from dark forces in both worlds.
One possible plot could be that there is a powerful, ancient magic that links the two universes. Harry Potter and Gaara are unknowingly brothers due to this magic. A dark entity threatens both worlds, and only by combining their powers and the knowledge of their two different cultures can they defeat it. Along the way, they have to overcome their differences in personality and upbringing. Harry, who grew up in the wizarding world, has to understand Gaara's more harsh and lonely upbringing in the Hidden Sand Village. And Gaara has to adapt to the more complex social and magical structure of the Harry Potter world. They would form a bond stronger than just brotherhood as they fight side by side against the common enemy.
The plot might start with their shared origin. Maybe they were separated at birth due to some dark magic or a mutant - wizard conflict. As they grow up separately, they develop their own powers and personalities. Then, through a series of events, they are brought together. They could face a common enemy that is a threat to both the wizarding world and the mutant world. Along the way, they learn about each other and their shared family history, and they start to build a relationship as brothers.
Well, perhaps she grows up in a different environment than Harry, away from the Dursleys. This different upbringing shapes her character in a unique way. She might have a natural talent for a particular type of magic that Harry doesn't. For example, she could be really good at divination and use her skills to foresee the coming dangers to Harry and the wizarding world. And she would be constantly trying to keep her identity as Harry's sister a secret from the wrong people while still trying to support him in his fight against evil.
One possibility is that he would use his prior knowledge to prevent the tragedies that befell his family. He could also have a different dynamic with Sirius and Remus, as he'd be part of James' inner circle from the start.
One possible storyline is that the OC, as Harry's brother, has a special gift that sets them apart from Harry. This gift could either be a help or a hindrance in their adventures. For instance, it could be a unique form of magic that is not commonly seen in the wizarding world. They would have to learn to control it while also dealing with the threat of Voldemort. And their relationship with Dumbledore could also be different. Dumbledore might see the OC as a key to a different solution to the Voldemort problem.
Yes, there might be. The world of fanfiction is vast and diverse. There are many creative writers who come up with all sorts of interesting and unexpected crossovers. It's possible that someone has written a story where Harry Potter is Chuck's brother, exploring how their relationship would impact the Harry Potter universe and whatever world Chuck is from.