This fanfiction concept is really interesting. Harry being Draco's younger brother would mean a different upbringing for Harry. He'd have access to the Malfoy's wealth and status. However, his personality might still shine through. He might be a Slytherin with a heart of gold, trying to change the family's views from the inside. His relationship with Dumbledore would also be different as Dumbledore might see him as more of a 'project' to save from the Malfoy influence.
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.
Well, it would change a lot. For one, Draco's family would have a different connection to Harry. Instead of being rivals, they might be more protective of Harry. Draco could use his pure - blood status to shield Harry from some of the prejudice in the wizarding world. Also, the whole dynamic at Hogwarts would shift. Draco might be more like an older brother figure to Harry, guiding him in certain aspects of magic and school life, which would be very different from their original hostile relationship.
Well, it would change everything. For one, Draco's attitude towards Harry might be different. He could be conflicted between his loyalty to his Slytherin friends and this newfound family connection. And Harry, he'd have to deal with the fact that he has a son who was once his enemy. The whole dynamic at Hogwarts would shift, and the battles between Gryffindor and Slytherin might take on a whole new meaning, as they are now sort of family - in a very strange way.
If Harry were Draco's older brother in this fanfiction, their relationship at Hogwarts would be a total mess - up of the original dynamic. Harry would be constantly torn between the Gryffindor values he adheres to and his family bond with Draco. Draco might start to question his Slytherin - only ideology because of his connection to Harry. For example, they might find themselves in situations where they have to choose between their house loyalties and their new - found brotherly bond, like during the Quidditch matches or the Triwizard Tournament.
Well, it could change a lot. For one, Draco might not be as mean to Harry as he was originally. Since they're brothers, there could be a sense of family loyalty that stops Draco from siding with the Death Eaters. Harry would also have more support within the Slytherin house through Draco, which could change the whole dynamic between the houses.
Well, it could change the story in many ways. For example, if the younger brother is as magically talented as Harry, they might share the spotlight at Hogwarts. He could also be a support system for Harry, especially during tough times like facing Voldemort. Maybe he'd have different relationships with the other characters, like befriending Ron and Hermione in a different way than Harry did.
In this fanfiction, Harry could have a very different personality. Growing up as a Malfoy, he might be more reserved and proud at first. However, his inherent goodness from the original story would still shine through. There could be interesting dynamics between him and Draco. They might have a love - hate relationship where they compete but also secretly care for each other. Harry could also use his position in the Malfoy family to try and change some of their more negative attitudes towards non - pure - blood wizards.
If Hermione and Draco were siblings in fanfiction, it would completely turn the original story on its head. For one, Hermione's Gryffindor nature and Draco's Slytherin one would create a really interesting family dynamic. Their parents must have had a very complex relationship for this to be possible. It could lead to Hermione having a different view of the wizarding world from the start. Instead of being a Muggle - born advocate in the way she was, she might have had some internal conflict due to her Slytherin - influenced family ties. And Draco might not be as much of a bully as he was originally, or at least he would have a different kind of relationship with Harry, Ron, and Hermione.
The twin could change the plot by being more interested in academic magic than Harry. This might lead to him uncovering secrets in the library that Harry misses, which could be crucial in the fight against Voldemort.
His brother could introduce new alliances. If he's more friendly or has different views from Draco, he might make friends with characters that Draco wouldn't usually associate with. This could lead to new storylines where Draco has to deal with these unexpected connections.