Isabella as a Malfoy would likely change the dynamic in a fanfic quite a bit. Firstly, she could introduce a new form of relationship between the Malfoy family and Harry Potter. Maybe she has a secret admiration for Harry and tries to protect him from her own family's plots. This would add a strange sort of tension where the Malfoy family is both a threat and a place where there is an ally for Harry, in a way. Also, she could influence other characters in the Malfoy family. If she starts to show different values, it might make Draco, for example, question his own actions more. This could lead to a different path for Draco in the fanfic, perhaps one where he doesn't fully follow in his father's footsteps.
She could make the Malfoy family seem more complex. Instead of just being the 'bad guys', with Isabella there could be some internal family debates about right and wrong.
If Isabella is a Malfoy in a Harry Potter fanfic, the power dynamics within the Slytherin house would shift. Usually, the Malfoys are seen as leaders among the Slytherins. But if Isabella has different values, she could split the Slytherin students. Some might follow her more progressive ideas, while others would stick to the traditional Malfoy - like views. This would create a whole new political situation within the Slytherin house. Also, in the overall wizarding world, her presence as a Malfoy who doesn't conform could inspire other pure - blood families to question their long - held beliefs. It could start a movement towards more acceptance and equality in the wizarding community that we didn't see in the original books.
She might be a Malfoy who has a change of heart. Maybe she starts to question the pure - blood supremacist views of her family. She could secretly befriend Harry Potter and his friends, providing them with inside information on the Malfoy family's plans.
The Malfoy family would have to reevaluate their pure - blood ideology. Having Harry, who is a symbol of the defeat of pure - blood supremacist Voldemort, in their family would be a big shift. They might become more open - minded towards non - pure - blood wizards. Also, their relationship with the other Death Eaters would be strained as Harry is their enemy.
Fanfics change their relationship by creating situations where they have to rely on each other. For example, they might be trapped in a magical maze together and need to cooperate to get out. This forces them to see each other in a new light.
It could add more complexity. If she's older, she might be more in control of the family's image and decisions, which could put Draco in a different position within the family. He might feel overshadowed or have to prove himself more.
Well, if Harry was Lucius Malfoy's son, it would completely flip the story. Harry would be brought up in a pure - blood supremacist family. He might not have his kind heart as we know it. His relationship with Ron and Hermione would be non - existent or very different. He would probably be taught dark magic from a young age instead of the values he learned at Hogwarts in the original story.
Their relationship could start with mutual suspicion. Harry is wary of Evangeline because she's a Malfoy, and Evangeline is hesitant about Harry due to his reputation as the 'Chosen One'. But as they are forced to work together on a school assignment, they start to see each other's true natures. They gradually become friends and confidants, sharing their fears and hopes.
In a fanfiction where Harry is Draco's brother, it would be a wild shift in the story. The sorting ceremony might have been really interesting. Harry could have been conflicted between Gryffindor and Slytherin. His friends in Gryffindor might have been very suspicious of him at first. His relationship with Sirius would also be strange. Sirius hated the Malfoys, so would he still be as fond of Harry? And Harry's magical abilities might have been nurtured in a different way, perhaps more towards the Dark Arts, which could have made him a very different kind of wizard.
In fanfiction, Astoria can also be a catalyst for change in the political and social aspects of the wizarding world. Coming from a well - known Slytherin family, she might have influence. If she teams up with Harry, they could work towards reforming the Ministry of Magic. Her presence can make the story explore themes like redemption for Slytherin - related characters and breaking down the long - standing prejudices between houses and different wizarding families.
If Harry was Lucius' son, the story would be turned upside down. His appearance might even change, as he'd inherit some Malfoy features. His Hogwarts house would most likely be Slytherin. In the original story, Harry was a symbol of hope for the non - pure - blood wizards. But in this fanfic, he'd start off as part of the pure - blood elite. His relationship with Draco would be a brotherly one, which would be really strange considering how they were enemies in the original. The Triwizard Tournament might not happen as it did, or Harry might participate in it with different motives, perhaps to prove his worth to the Malfoy family rather than for the glory of Hogwarts.
The fanfic changes the moral compass of the story. The original story promotes love, acceptance, and unity between different groups. If Harry hates Muggles here, it sends a very different message. It might make the story more about division and prejudice, which is a huge departure from the positive themes of the original Harry Potter series. This would also likely change the way other characters interact with Harry, as they may not support his new - found hatred.