In fanfiction, Fenrir might be possessive of Hermione because she represents something he lacks. Maybe he's drawn to her purity or her connection to the wizarding world in a way that he wants to own it through her. It could also be a form of power play, where having Hermione under his control gives him more status in the dark and twisted world he inhabits.
One reason could be that Fenrir sees Hermione as a unique and powerful individual. Her intelligence and magic might attract him in a way that makes him want to possess her, as if she's a prized possession that no one else can have.
In fanfiction, Tom Riddle may be possessive of Hermione because she represents something he can't fully understand or control. Her moral compass is so different from his. He may think that by possessing her, he can gain some of that goodness or use it to his advantage. Also, Hermione's popularity and influence among her peers might make Riddle want to have her as a trophy of sorts, to show his superiority over others in the wizarding world.
Maybe it's because Hermione has unique qualities. Her intelligence and strength might attract James, and his possessiveness could stem from a fear of losing someone so special.
Finding fanfictions with this exact dynamic can be a bit tricky. You could start by joining relevant fan communities on social media platforms or forums dedicated to the fandom. There, you can ask fellow fans if they know of any such stories. They might be able to point you to some hidden gems that deal with Fenrir's possessiveness towards Hermione.
One possible reason could be envy. Maybe Fleur sees Hermione's intelligence and skills and feels threatened. So she becomes possessive to try and keep Hermione in a certain place or relationship where she can control her influence. Another reason might be that Fleur has some deep - seated insecurities. Hermione is well - liked and respected in the wizarding world, and Fleur, perhaps unconsciously, wants to claim Hermione as 'hers' to boost her own status. It could also be a case of misinterpreting friendship for something more possessive. If they are friends in the fanfic, Fleur might not know how to handle her strong feelings for Hermione in a healthy way and ends up being possessive.
One possible plot could be the challenges they face. Maybe Hermione is initially scared and conflicted about the pregnancy as Fenrir is a complex and somewhat dangerous character. Society might not accept their union, so they have to deal with secrecy and the judgment of others.
Maybe he is attracted to Hermione's character traits like her intelligence and courage. Fanfictions often explore different aspects of her personality in unique ways that might intrigue him.
One reason could be that Theo really admires the character of Hermione. In the original stories, Hermione is intelligent, brave and resourceful. Fanfictions might explore different aspects of her character that the original doesn't fully cover, which could be fascinating for Theo.
One possible reason could be that he has some sort of hidden agenda. Maybe he wants to use Hermione as a bargaining chip later. Another reason might be that there is some magic or force compelling him to do so against his will. It could also be that he has a momentary change of heart, perhaps seeing something in Hermione that reminds him of a past acquaintance or a long - lost bit of humanity within himself.
In some fanfictions, Ron gets jealous when Hermione spends too much time studying with other classmates. He might give her the cold shoulder or make snide remarks about her study partners.
One possible reason could be a powerful spell gone wrong. Maybe she was caught in the crossfire of a dark magic spell that Snape was either trying to counter or was involved in accidentally. Another reason might be extreme emotional shock. For instance, if she discovered some dark secret about Snape that was so overwhelming it sent her into a catatonic state.