There could be Edward. Even though the focus is on Carlisle and Bella, Edward's presence might still be felt as he was an important part of Bella's life before. His reactions to Carlisle and Bella's relationship could add some drama.
The Cullen family members are important characters too. Edward, for example, might have an interesting dynamic with Bella in this fanfiction. He could be either protective or jealous of Carlisle's special relationship with her.
One possible plotline could be Carlisle teaching Bella more about the history and ethics of the vampire world. For example, he might take her on trips to ancient vampire sites and share stories passed down through the ages.
Well, of course, there's Dark Carlisle, who might be a character with a shadowy past and different moral compasses compared to the regular Carlisle. And then there's Bella. She is often portrayed as the one who tries to understand Dark Carlisle, bringing out different sides of him. There could also be other supporting characters from the Twilight universe, like the other members of the Cullen family, who might react differently to Dark Carlisle and Bella's relationship.
In some fanfictions, other members of the Cullen family can also be important secondary characters. For instance, Edward might play a significant role. He could be either a source of conflict, as he has his own feelings for Bella, or a mediator, trying to understand the strange attraction between Carlisle and Bella. Also, Esme, Carlisle's wife in the original story, could be a character that adds more complexity to the situation. Her reaction to Carlisle's feelings for Bella could range from heartbreak to acceptance, depending on how the author writes it.
In the fanfiction, Carlisle's sense of duty to his family and the vampire code might be a hurdle. He has to balance his feelings for Bella with his responsibilities to the Cullen family. Also, Bella's own human life and her relationships with other humans, like her father, could be a complication. How can she maintain those relationships while being in love with Carlisle? There's also the issue of secrecy. Their relationship has to be kept hidden from the outside world to protect both of them.
Often, it starts with an unexpected encounter or a moment of realization. Maybe Carlisle sees Bella in a new light, not just as Edward's girlfriend but as an individual with her own charm. Then, there are small gestures of kindness and understanding between them that gradually build up the relationship.
Mainly, it's Carlisle, a sophisticated and noble vampire, and Bella, a character full of curiosity and love. Their relationship is central. But we can't forget about the other vampires in their world. For example, Edward could be an interesting character in this fanfiction. He was once in love with Bella, and his reaction to her being with Carlisle could add a layer of drama. Also, Esme, Carlisle's adoptive mother in a sense, could play a role in either accepting or having some doubts about their union.
In some fanfictions, their relationship might start with Carlisle being drawn to Bella's unique spirit. He, as an older and more experienced vampire, is intrigued by her resilience. Maybe he first notices her when she enters the Cullen family's orbit, and from there, a slow - burning attraction begins to form as they interact more and get to know each other on a deeper level.
Definitely not. Fanfiction should be a creative and positive exploration of the existing story and characters. 'Dirty' content in it can distort the image of the characters and the overall atmosphere of the story, and may also violate the respect that should be given to the original work.
Because he sees her as a fragile human in a dangerous vampire world. He has a sense of morality and doesn't want her to get hurt.