Well, it could be a relationship full of mutual understanding. They would likely share their secrets and fears with each other easily. Maybe Bella would introduce Didyme to her human friends in a way that's different from how she interacted with other vampires in the original story. They could also have a relationship where they constantly challenge each other to grow, like Didyme teaching Bella more about vampire culture and Bella showing Didyme new perspectives from her human upbringing. This would make for a really interesting and complex relationship dynamic in the fanfiction.
Typically, in fanfiction, their relationship as mates could involve a lot of unspoken communication. They would be attuned to each other's moods. There might be a lot of tender moments between them, like soft touches and long glances. Since Didyme is a vampire and Bella has her own unique position in the Twilight world, they may face some external challenges as a couple. Other vampires might not accept their relationship easily, or there could be some danger from the Volturi. This would only strengthen their bond as they face these difficulties together.
One fanfiction you could look for is on Archive of Our Own (AO3). Just search for 'Bella and Didyme mates' in the search bar there, and you'll likely find some relevant works.
Their relationship could start with mutual curiosity. Arthur is used to the underwater world and Bella is from a world of vampires and werewolves. They would have to learn about each other's cultures and abilities. As they spend more time together, they would develop a deep trust. For example, Arthur might show Bella the beautiful coral reefs in his world, and Bella could introduce Arthur to her friends in Forks. This sharing of their worlds would bring them closer and strengthen their bond as mates.
Well, in these fanfictions, a common plotline is the power struggle. Aro is a powerful vampire, and Bella, even as a vampire, has her own strengths. Their relationship might be about finding a balance of power. Another plotline could be the discovery of their mate bond. How did it happen? Was it some long - lost prophecy or just a random twist of fate? And then there's the matter of their different worlds colliding. Bella is from a small town in Forks, while Aro is at the center of the vampire world. How do they bridge this gap? There could be a lot of cultural differences, so to speak, between the two of them that need to be explored in the story.
In the fanfiction, their relationship development could be based on mutual discovery. Harry discovers Edward's noble side and his sense of loyalty. Edward, in turn, discovers Harry's hidden courage and kindness. They start to communicate more openly, sharing their fears and dreams. This sharing deepens their bond, and they begin to support each other in every aspect of their lives. For example, Harry helps Edward with his family issues, and Edward helps Harry with his self - confidence. Eventually, they become an inseparable couple.
It would be really complex. Their parents would have to deal with two very different children. One is a demigod with powers and a connection to the Greek gods, and the other is a girl involved in the vampire - werewolf drama. There would be a lot of secrecy in the family, trying to hide Percy's demigod world from Bella's friends and vice versa.
The relationship could develop through shared experiences. For example, they could go on a hunting trip together. During this trip, they learn about each other's hunting styles and preferences. This shared activity can break the ice and start to build a bond.
In this fanfiction, the relationship could start with a simple attraction. Esme might be drawn to Bella's unique human - turned - vampire essence. As they become mates, they could travel together, exploring different parts of the world. Along the way, they encounter other supernatural beings. Their bond is tested when Bella is put in danger, and Esme has to use all her strength and wits to save her. This experience deepens their relationship and they become even closer, vowing to always protect each other.
Their relationship could be developed uniquely by having them communicate in a special way. For instance, instead of just talking, they have a mental connection that only they share. This connection allows them to understand each other's feelings and thoughts deeply, which helps them face the challenges in the gp.
It would likely shock and confuse many characters. For example, Edward would be very surprised and perhaps a bit jealous as he had a strong relationship with Bella. The Cullens as a family might be divided in their opinions. Some, like Esme, might be more accepting and try to understand, while others could be more hesitant. The werewolves would also be affected. They might see this as another strange and unpredictable aspect of the vampire world and it could potentially change their relationship with the Cullens. Jacob, in particular, would probably be very confused about Bella's new situation.
I'm not sure specifically about a fanfiction involving all of them. But you could start by looking on popular fanfiction websites like Archive of Our Own. Try searching for their names together and see what pops up.