Well, Hermione being James' adopted sister would likely make her closer to Sirius. Sirius might see her as a little sister figure too. He could be protective of her, much like he was with James. They might share a special bond over their love for James and their shared experiences within the wizarding world.
Hermione's relationship with Sirius would also be affected by her relationship with James. If there were any disputes between James and Sirius, Hermione might find herself in the middle, trying to play peacemaker. She would use her diplomatic skills to try and resolve any issues, which could either strengthen or strain her relationship with Sirius depending on how the situations play out.
Well, Hermione being James' twin sister would make her and Sirius have a tight - knit relationship. Sirius would be part of her family in a way. He'd be there for her during her Hogwarts years, and they could bond over their shared love for James. Sirius might also teach Hermione some of the more secretive and dangerous spells that the Marauders knew, and Hermione would keep Sirius in line with her logical thinking and rules - following nature, creating a balanced and loving relationship.
Hermione's academic performance might improve even more. Sirius could provide her with rare books and knowledge from his family's library. For example, there could be ancient spells and magical theories that are not commonly known. This would give her an edge in her classes.
One possibility could be that Sirius sees Hermione's intelligence and determination and decides to take her under his wing. Maybe he realizes her potential and wants to protect her from the dangers in the wizarding world that he has faced himself.
Often, it begins with Hermione trying to help Sirius deal with his post - Azkaban trauma. She uses her knowledge and compassion to reach out to him. As he heals, he starts to see her in a new light. Their relationship then grows as they start to understand each other better. The lemon parts usually are used to explore their more passionate and private moments, which are often written in a very tender and intense way, adding a new dimension to their relationship.
It could potentially strain the relationship. If Sirius misinterprets the situation, it might create some tension. Harry and Hermione would feel like they need to explain themselves, and Sirius might be a bit standoffish until he gets the real story. For instance, if he thought they were hiding something from him, it could make things a bit rocky between them for a while.
She would probably be more rebellious. Sirius was always against the status quo at Hogwarts. So, Hermione as his daughter would likely question the rules more often. Instead of strictly following the school regulations like in the original story, she could be at the forefront of student protests or challenges to the faculty's authority. She would also have a more devil - may - care attitude towards her grades, focusing more on the knowledge itself rather than the academic recognition.
One possible plotline could be Hermione growing up in the wizarding world with James as her brother. They might get into all sorts of magical mischief together at Hogwarts. Maybe she uses her intelligence to help James and his friends out of tricky situations, much like she did with Harry and Ron in the original series.
It would likely make her more self - assured. Sirius would constantly be there to support her and tell her she's capable. This could lead to Hermione being even more outspoken and confident. Instead of just arguing her points in the classroom, she might start challenging the wizarding world's old - fashioned ideas more publicly. Also, she might develop a stronger sense of loyalty to those she cares about, like Sirius, similar to the loyalty he showed to his friends.
Their relationship might start off rocky due to the forced nature of the marriage law. Sirius could be overprotective at first, seeing Hermione as someone he needs to shield from the dangers of his world. Hermione, on the other hand, might be frustrated by his overbearing attitude. But as time passes, they learn to communicate better and understand each other's strengths.
In this fanfiction, Hermione would grow up with a strong female role model. This would make her even more assertive in fighting for what she believes in. She may also inherit some of McGonagall's no - nonsense attitude towards things like Dark Magic and injustice. Her academic pursuits would still be important, but she might also focus more on the well - being of Hogwarts as a whole, similar to how McGonagall cares for the school.