Another theme is the development of their characters. Fanfic writers like to expand on Jasper's backstory and how Bella can influence or be influenced by him. For example, Jasper's past as a Confederate soldier might be explored in relation to Bella's modern - day values, and how they bridge that gap.
The struggle against the supernatural world around them is also common. They have to deal with other vampires, werewolves, and the secrets of the Twilight - like setting. For example, in some fanfics, they have to fight against a new threat that targets their relationship.
Another theme is the power dynamics. Caius being from one group and Jasper from another, there's often a play on power and how it affects their relationships with Bella. For example, in some fanfics, they compete for dominance in Bella's life while also trying to co - exist. This creates a lot of tension and drama which is very engaging for readers.
The theme of family is also present. They may not be related by blood, but in these fanfics, they create a family - like bond. They support each other, protect each other, and are there for each other in difficult times. This family - like bond is often a central aspect of the story, and it helps to drive the plot forward as they face challenges together.
One common theme is the exploration of the supernatural. Since Jasper has his own special abilities and the black swan concept often has a touch of the supernatural, it's often a part of these fanfics. For example, in many stories, Bella might discover some new, hidden side of Jasper related to the black swan idea.
Another theme is the power dynamic. Jasper has his special abilities and Bella has her own charm. Fanfictions may play with how these two aspects interact and influence each other. For example, in some stories, Bella's humanity affects Jasper's view on his vampiric nature.
A prevalent theme in jasper and bella fanfiction is the struggle against the odds. They come from different backgrounds and have different natures within the Twilight universe. Fanfictions often focus on how they overcome these differences. Also, themes of loyalty and sacrifice are common. They might be in situations where they have to be loyal to each other and make sacrifices for their relationship or for the greater good of their vampire - human world.
Romance is a very common theme. Writers often explore the relationships between these characters in a romantic context. Another common theme is adventure, where they might go on quests or face challenges together.
One common theme is friendship. They often have to learn to trust and rely on each other.
Another theme is the impact on the Cullen family dynamic. Their relationship, if they are related, can change the power balance and the way the family functions. It can also cause tensions or bring new understandings among the family members.
One common theme is the exploration of an alternative relationship. Since in the original 'Twilight' series, Bella is mainly focused on Edward, fanfictions often look at what could happen if she had a stronger connection with Jasper. Another theme is the power dynamic. Jasper's ability to control emotions and Bella's resistance to it can create some really interesting scenarios.