Well, it might be because in the fanfiction world, Hermione is often portrayed as this amazing, multi - faceted character. If she and Remus have a special connection, Tonks, who loves Remus, could get jealous. Maybe they are involved in some important magical research together or have a deep emotional understanding that Tonks feels she lacks with Remus. And Tonks, being a passionate person, can't stand seeing someone else getting so close to the man she loves.
In fanfiction, Tonks could be jealous of Hermione and Remus because of the way their characters interact. Remus is a complex and often lonely character. If Hermione is able to reach out to him in a way that Tonks hasn't been able to, it can stir up jealousy. For example, Hermione might be able to comfort Remus about his werewolf nature in a way that makes him open up more than he does with Tonks. Tonks, who loves Remus deeply, would then feel envious of the bond they share.
One reason could be that Tonks has feelings for Remus. In the story, if Hermione and Remus have a close relationship, perhaps a friendship that Tonks misinterprets as something more, it could make her jealous. Hermione is very intelligent and if she and Remus share a bond over knowledge or magic, Tonks might feel left out. Also, Tonks might be insecure about her own relationship with Remus and see Hermione as a threat.
Hermione is also highly respected by the teachers and other authority figures. She's often given important tasks and responsibilities. Tonks, on the other hand, might feel that she doesn't get the same level of recognition. So, in the world of fanfiction, this could be a reason for her jealousy towards Hermione.
Maybe it's because Hermione represents a new beginning for Lupin. She has a different energy compared to Tonks. Lupin could be drawn to Hermione's thirst for knowledge and her ability to look at things from a unique perspective. In fanfiction, the author can create all sorts of reasons, and this could be one of them.
It might also be that Hermione represents something Draco lacks. She is intelligent, confident, and has a strong moral compass. In fanfiction, Draco could be obsessed with her because he secretly admires these qualities and wants to be closer to someone who has them. He might see her as a challenge or someone who can change him for the better.
Perhaps Remus first notices Hermione's kindness towards him regarding his werewolf condition. She doesn't shy away but instead tries to find ways to help him. This kindness grows into something more, and they start to share their feelings. Their relationship could develop as they face challenges together, like dealing with the prejudice against werewolves. Hermione's strong will and Remus' experience combine to make them a formidable pair in the fanfiction.
It can add drama. Tonks might start acting out of character, being more cold or distant towards Hermione or even Remus. This can create tension in the relationships. For example, she might try to sabotage their friendship by spreading rumors or trying to keep them apart.
In many fanfictions, Remus might be protective of Hermione because he sees her great potential and intelligence. He could also feel a sense of duty as an older, more experienced wizard. Additionally, he may have witnessed some of the hardships she has faced at Hogwarts and wants to shield her from further harm.
One idea could be to focus on how they prepare for the baby's arrival. Maybe Remus is worried about his werewolf condition affecting the child, and Tonks has to constantly reassure him. They could start decorating the nursery with magical elements.
In fanfiction, their first encounter might be reimagined in various ways. It could be a chance encounter in Diagon Alley, where they bump into each other and there's an instant spark. Tonks' colorful hair and Remus' calm demeanor could create an interesting contrast from the start.
In some fanfictions, Remus Lupin might be hard for Hermione because of their age difference. Lupin is much older, and this can create complex power dynamics and social taboos in the relationship. Also, their personalities are quite different. Hermione is highly studious and often by - the - book, while Lupin has a more laid - back and world - weary nature, which could lead to clashes and difficulties in their interactions.
There might be some out there. You could start by looking on fanfiction platforms like Archive of Our Own. Just search for the relevant tags. However, this kind of pairing can be a bit of a crossover or AU (Alternate Universe) since in the original series, Remus has a relationship with Tonks, not Hermione. But fanfiction often plays with different pairings and scenarios.