The relationship would add a new layer of complexity to the story. It could lead to new plotlines about Hermione's family history. There might be secrets within Sirius's family that now relate to Hermione. For instance, there could be a family heirloom that has special powers which Hermione now has a claim to. This could attract the attention of dark wizards who want to steal it. It would also change the dynamic at Hogwarts. Teachers might treat Hermione differently knowing she has a connection to the infamous Sirius Black, and some students might be jealous or curious about her newfound family connection.
In Hermione's storyline, it could potentially change her future plans. Instead of just focusing on the wizarding world's problems, she might be more involved in Clint's world's affairs. This could mean she gets involved in battles against supervillains. For Clint, it might change how his character is perceived. He's known as a tough superhero, but now having a niece like Hermione, he could show a more nurturing side. Also, the magic from Hermione's world could seep into Clint's world, changing the dynamics of how things work there. For example, the use of magic spells to solve problems that were previously only solvable by technology or superpowers.
She could impact the storylines by changing the relationships. For instance, if she befriends Hermione early on, she might encourage Hermione to pursue different areas of study, which could then affect how Hermione helps Harry in later events.
It would likely create a lot of chaos. Sirius Black is already a bit of a wildcard in the Harry Potter world. If he becomes like the Joker, the sense of safety at Hogwarts would be completely shattered. Students would be constantly on edge, not knowing what he'll do next. The teachers would have a hard time controlling him, and it could even lead to changes in the power dynamics between different houses.
If Hermione was Remus' sister, her relationship with Harry and Ron would be affected. Harry might view her in a new light, as she now has a connection to one of his former teachers. Ron might be a bit jealous at first, but then realize it doesn't change who Hermione is. And her relationship with the other Hogwarts professors would also shift, as she has a closer family tie to Remus.
They could go on an adventure to find a lost family heirloom. This heirloom might be a powerful magical object that was lost during the First Wizarding War. Sirius, with his knowledge of the era, and Hermione, with her research skills, would make a great team to track it down.
Well, in fanfiction, the idea of Hermione being Voldemort's niece might stem from some sort of magical tampering with family lines in the past. It could be that a powerful spell was cast long ago that altered the relationships in a way that made Hermione related to Voldemort. Or it could be a completely different take on the lore where the wizarding world has a whole other layer of hidden family connections that JK Rowling didn't explore in the original series.
Well, if Hermione were Sirius's daughter in fanfiction, it would change a lot. For one, Hermione might have had a very different upbringing. She could have grown up with more knowledge about the wizarding world's secrets from Sirius. And in the Hogwarts years, her relationship with Harry and Ron might have been more complex. Maybe she would have been more involved in the Order of the Phoenix affairs earlier. Also, her magical abilities might have been influenced in different ways, as Sirius was from an old and powerful wizarding family.
In fanfiction, Harry Potter's magic might introduce a new cultural element. The wizarding world has its own traditions and values. This could influence the characters in the Marvel Universe. For instance, the concept of house loyalty from Hogwarts might be adopted by some superhero teams. Also, the magic could add new types of challenges. Magic - based threats might emerge that the Marvel heroes are not used to dealing with, like dark wizards or magical creatures.
The impact would be huge. For one, the entire wizarding world's view of Hermione would change. She has been a symbol of intelligence and a key part of the fight against Voldemort. If she is his daughter, it would make the wizarding community question everything they knew. Dumbledore's plans might also be thrown into chaos. He had always counted on Hermione as an ally, and now he would have to reevaluate her role. The power dynamics at Hogwarts and in the wizarding world at large would be completely different, with Hermione being both a potential threat and a possible asset depending on which side she chooses to embrace.
Well, in fanfiction, anything can be possible. Maybe it could be a result of some time - turning magic gone wrong. Or perhaps there was a secret relationship between Sirius and Hermione's mother that was never revealed in the original story. It's all about creative interpretations in fanfiction.