Harry might become more cautious. With Draco as his brother, he'd be exposed to Slytherin - like thinking more often. He could start to weigh his actions more carefully and think about the long - term consequences. Draco, on the other hand, might become a bit more empathetic. Growing up with Harry, he'd see the Gryffindor values up close and might start to care more about others.
Well, Harry would likely develop a more diplomatic side. Since he and Draco are siblings, he'd have to deal with Draco's Slytherin friends and their ways. This would force him to be more tactful. Draco would probably become more open - minded. Harry's experiences with different kinds of magic and people outside of Slytherin would make Draco realize that there's more to the wizarding world than what he was taught. He'd start to question some of the pure - blood dogma he grew up with and become more inclusive in his thinking.
In this scenario, Harry could lose some of his impulsive nature. Draco's influence would make him consider different strategies. He might also become more aware of the politics within the wizarding world, as Draco would be more attuned to that. For Draco, his arrogance could be toned down. Harry's sense of justice and fairness would start to rub off on him, making him more approachable and less likely to look down on others.
Hermione's personality might change in that she would have to be more diplomatic. Instead of always speaking her mind bluntly as she usually does, she'd need to consider Draco's feelings and the situation of their arranged marriage. She could become more patient too. For Draco, he might become more self - reflective. Being married to Hermione, who is so different from him, would force him to look at his own prejudices. He could develop a more humble side as he realizes that Hermione has a lot to offer despite being a Muggle - born.
In these fanfictions, Draco's arrogance usually takes a backseat. The betrothal forces him to interact with Hermione on a deeper level, and he realizes that there's more to her than just being a 'Mudblood' in his old view. His personality becomes more complex as he tries to balance his Slytherin pride with his new - found feelings for Hermione. Hermione, on the other hand, might become a bit more secretive. She has to deal with her new relationship with Draco while also maintaining her friendships, and she may not be as open with her friends about her true feelings for Draco at first.
In these fanfictions, Harry may develop a more diplomatic side to his personality. Since Draco is from Slytherin and has a different way of thinking, Harry has to learn to negotiate and find middle ground. For Draco, his friendship with Harry can make him more empathetic. He might start to care about the well - being of others outside of his Slytherin clique, like the Gryffindors and other Hogwarts students, which is a big change from his initial self - centered attitude.
Draco might become more open - minded. Luna's free - spirited and accepting nature could influence him to let go of some of his Slytherin prejudices. He might start to see the beauty in things he previously dismissed. For Luna, she could become more assertive. Draco's confidence (even if it was sometimes misdirected in the past) could rub off on her, and she might be more vocal about her ideas and beliefs in their relationship.
Harry's personality could shift towards being more introspective. He would constantly be thinking about the implications of being a Riddle. His sense of justice might still be strong, but he could be more cautious in his actions. Draco might experience a major change. He might lose some of his arrogance as he realizes that being a Riddle doesn't automatically mean power and privilege. Instead, it comes with a lot of baggage. He could become more collaborative, working with Harry instead of against him, and might even show more kindness towards those he previously looked down upon.
Often in these fanfictions, a change in the overall plot of the wizarding world can impact their relationship. Say, if Voldemort never existed in the alternate universe. They might be academic rivals instead of the more hostile enemies from the original story. They could end up respecting each other's magical abilities and form a bond over that. Another way is if they are both part of a prophecy in the alternate universe that forces them to work together, which can lead to a whole new dynamic in their relationship.
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.
Harry might become more relaxed around Draco. He's used to being on guard against Draco's taunts, but as friends, he lets his guard down. He may start to show his more humorous side and not be so serious all the time. For Draco, he could become less arrogant. He realizes that Harry isn't just the 'Chosen One' to be hated but a real person with his own struggles. He might start to be more empathetic, which is a big change from his usual self - centered attitude.
In the coven, Harry could start to show a more possessive side. Since vampires are often associated with territoriality, he might become overly protective of certain things or people within the coven. Draco might develop a more empathetic side. He could start to understand the struggles of others better, especially if he sees Harry, his former rival, also trying to fit in. The new environment of the coven forces them both to re - evaluate who they are and how they interact with others.
In this scenario, Severus' character experiences a significant transformation. He has to shed his cold exterior to a large extent. He becomes a father figure, which means he has to be there for the boys emotionally. He starts to show emotions more openly, whether it's pride when they do well in their studies or worry when they are in danger. His sense of loyalty also shifts. Before, it was mainly towards certain people or causes, but now his loyalty is first and foremost to Harry and Draco. This new - found loyalty makes him a more rounded and likable character in the fanfiction, as he is no longer just the brooding potions master but a loving and dedicated father.