One common theme is their relationship. Writers often explore how Remus and Tonks got together, their initial attraction, and how they dealt with the challenges in their relationship, like Remus's self - doubt due to his werewolf condition.
One possible scenario in this fanfiction could be that Teddy shows some unique magical abilities that remind Remus and Tonks of their own magical heritages. Maybe Teddy can transform in a way that combines both werewolf and metamorphmagus traits, which would be a really interesting plot point. It could also explore how Remus and Tonks, who had such a tragic end in the original story, get to experience some happy moments with their son Teddy through the magic of fanfiction.
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.
Their relationship in fanfiction is appealing because it's a story of two very different characters coming together. Remus, with his more reserved and self - doubting nature, and Tonks, who is bold and vibrant. It's like the classic 'opposites attract' scenario.
You can start by looking on popular fanfiction websites such as Archive of Our Own (AO3). It has a vast collection of fanfictions from various fandoms, including ones about Remus Tonks. Another option could be Fanfiction.net, although the tagging system there might require a bit more searching to find exactly what you're looking for.
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.
Well, it could be about Teddy having a dream where he meets his parents. In the dream, Remus and Tonks are as he's always imagined them. They tell him how proud they are of him, even though they didn't get to see him grow up. This simple encounter could be a very moving and emotional one, with Teddy waking up with a newfound sense of purpose and connection to his parents.
A great fanfiction idea could be one that shows how their love developed in secrecy. Maybe a story called 'Remus and Tonks: Hidden Love'. It could show the challenges they faced in a world where werewolves were not fully accepted and Tonks being an Auror. Their love had to be hidden at times, and such a story could explore those emotions and situations. There are also stories that might focus on their post - marriage relationship, like 'Remus and Tonks: After the Wedding' which could explore how they navigated life together.
There's also a fanfiction called 'Tonks' Pregnancy Trials'. In this one, it shows how Tonks deals with the physical and emotional aspects of being pregnant while also being in a rather complex wizarding world situation. It delves deep into her character and her relationship with Remus during this time. It's quite an engaging read as it weaves in elements of the Harry Potter universe's magic and mystery.
One popular fanfiction might be 'A New Beginning' which beautifully captures their first encounter in a very emotional and detailed way. It delves deep into their characters and the budding relationship between them.