A good plot could be them trying to solve the mystery of their parents' past. Since Hermione is a Muggle - born in the original story, this fanfiction could rewrite her backstory to be related to James. They could find out that their parents were involved in some sort of secret magical society that was disbanded years ago, and now they are facing threats from remnants of that society. Another plot might be that they both have a special connection to a magical creature. For example, they discover that they can communicate with a Phoenix that has been guiding their family for generations. They then have to protect the Phoenix from dark wizards who want to use its powers for evil.
One idea could be that as siblings, they discover a hidden magical ability that only runs in their family. For example, they might find out they can communicate with magical creatures in a unique way. This could lead them on an adventure to protect these creatures from dark wizards who want to use them for evil purposes.
Well, a possible plot could be that Draco and Hermione, as siblings, are both sorted into different houses at Hogwarts. They initially struggle with their loyalty to their houses while also trying to figure out their new relationship. There could also be a plot where they discover a common enemy within the wizarding world who is trying to harm their family, and they must use their combined skills to defeat this foe.
One idea could be that her siblings are also magically gifted but in different ways than Hermione. For example, one might be excellent at potion - making while Hermione is known for her academic knowledge. Another plot could be that they get separated at a young age due to some dark wizard threat, and the story is about their journey to find each other again. A third idea is that her siblings are muggles and Hermione has to keep her wizarding world a secret from them, which creates a lot of comical and tense situations.
A third plot could be centered around their different friend groups. James is likely to be friends with more mischievous types, while Hermione has her studious friends. Their sibling relationship could be tested when their friends' actions or opinions clash. But in the end, they realize that family is more important and find a way to bring their two worlds together.
One idea could be that Hermione travels back in time and accidentally changes something that affects James's future. Maybe she saves someone important to James that was supposed to die, and then they have to deal with the altered timeline together.
One challenge could be living up to their parents' expectations. If they come from a family with a long magical lineage, there might be pressure on both of them to be top students or powerful wizards. James might feel overshadowed by Hermione's academic achievements, or Hermione could feel left out when James gets more attention for his daredevil stunts.
Well, one unique idea is time - travel. In some fanfics, Hermione might use her intelligence to create a time - traveling spell that takes her and Harry back to the time of James and Lily. This allows for some really interesting interactions and changes in the timeline.
One popular story might be 'The Zabini - Granger Bond'. It delves into how Blaise and Hermione, as siblings, navigate the wizarding world together. Their different personalities, with Blaise's Slytherin cunning and Hermione's Gryffindor bravery, create interesting interactions.
Well, they could discover that their unborn child has some very special powers. This leads to a plot where they have to keep it a secret from certain dark forces in the wizarding world who would want to use the baby's powers for evil. They might seek the help of Dumbledore or other wise wizards to protect their child and figure out how to train the baby when it's born to use its powers for good.
One plot idea could be that they are forced into an arranged marriage by their families to end the long - standing feud between the pure - bloods and the Muggle - borns. At first, they resist but gradually discover they have more in common than they thought. Another idea is that they meet years after the war, both changed people. They start to work together on a project for the betterment of the wizarding world and fall in love during the process. A third plot could be a time - travel story where Hermione goes back in time and has to marry Draco to prevent a dark future from happening, and in the process, they develop real feelings for each other.