One possible plot twist could be that Jasper is being controlled by an external force, like a powerful vampire with mind - control abilities. So, he doesn't really mean to kidnap Bella in his true self.
It could be that Jasper's past somehow resurfaces and he believes that Bella is the key to solving some long - forgotten mystery or righting a wrong he committed in the past. So, in his desperation, he kidnaps her, thinking it's the only way to get to the truth or redemption.
One possible plot twist could be that Jasper discovers some hidden power or heritage in Bella that he wasn't aware of before. This could change how he views her and their relationship. Another twist might be that there's some sort of enemy from Jasper's past who targets Bella because of her relation to him. It could also be that Bella finds out some dark secret about Jasper that makes her question whether she can really trust him as a father.
Another idea is that the fanfiction could be a dark, alternate universe story where Jasper has turned evil. His reasons for kidnapping Bella could be tied to some sort of revenge plot against the Cullens. He might hold a grudge against them for something that happened in the past, and Bella is just a means to get back at them. This would create a very different dynamic compared to the original Twilight story.
Well, in this kind of fanfiction, a plot twist could be that an outside force tries to drive them apart by making them believe false things about each other. Maybe they are both in love with the same person, which creates a huge rift between them. Or there could be a situation where one of them sacrifices themselves for the other in a way that no one expected, completely changing the dynamic of their relationship.
Maybe Victoria has actually set a trap for Jasper while pretending to target Bella. So when Jasper goes to save Bella, he walks right into the trap. Or perhaps there's a misunderstanding and Bella thinks Jasper is working with Victoria at first, which adds a whole new layer of complexity to the story.
One possible plot twist could be that a long - lost relative of Bella shows up and tries to stop the wedding because they have some dark secret about the Cullens. Another could be that a new vampire coven arrives and challenges the Cullens right before the wedding, forcing Bella and Jasper to postpone it while they deal with the threat. Maybe there's also a twist where Bella discovers a new power within herself on her wedding day that changes the whole dynamic of the relationship with Jasper and the Cullen family.
Perhaps the story focuses on their journey of accepting the pregnancy. At first, they might be in shock and denial. But as time passes, they start to plan for the future. Bella could be worried about how her body will handle the pregnancy, especially if there are any differences due to Jasper's nature. They might also have to deal with the reactions of their friends. Some might be supportive, while others could be judgmental. The fanfiction could explore all these aspects in detail, from the emotional turmoil to the practical arrangements for the baby.
In this fanfiction, it could be that Bella has some unique quality that Jasper finds irresistible. For example, she might have a different perspective on life or a certain charm. As for Alice, she might start to suspect something is wrong when Jasper becomes distant. She could then start to investigate and discover the truth about Jasper's feelings for Bella.
A really interesting plot twist might be that Voldemort is being controlled by an even darker force, and Harry has to figure out a way to break that control while being held captive. Or perhaps Harry's friends, thinking he is dead, accidentally start a chain of events that end up helping Harry escape in a very unexpected way. For example, Hermione might cast a spell that was supposed to be for protection but ends up creating a portal right in Voldemort's lair.
The plot could take a turn where Zabini is initially seen as the bad guy because of the kidnapping, but in reality, he is trying to protect Hermione from a greater threat. Maybe there's a prophecy that involves Hermione and Zabini, and the kidnappers are trying to stop the prophecy from coming true. Another possible twist is that Hermione's kidnapping leads to a discovery of a long - lost magic that Zabini's family has been searching for. This magic could change the balance of power in the wizarding world, and now Hermione is in the middle of it all.
A really unexpected plot twist in this kind of fanfiction might be that the kidnapping was a mistake. The kidnapper was actually after someone else but got the wrong duck. This could lead to all sorts of comical or tense situations as they try to figure out what to do with the wrong captive. Also, the kidnapped character could discover a long - lost secret about their family during their captivity, which changes the whole dynamic of the story.