One interesting plot twist could be that the treaty has a hidden clause which changes the nature of their marriage completely. For example, it might initially seem like a simple political union, but the hidden clause reveals that they have to perform certain magical or supernatural tasks together to truly solidify the marriage.
Maybe there's a plot twist where an old enemy of Edward's uses the marriage treaty as a way to get to him. They try to manipulate Bella into believing that Edward has ulterior motives for the marriage, causing a rift between them until they discover the truth.
At first, it might be a bit rocky. Since the marriage is by treaty, they may be a bit wary of each other. But as they start spending time together, they could begin to discover common interests. For instance, they might both be interested in a particular type of literature or music, which helps to break the ice.
A really interesting plot twist could be that Bella's pregnancy progresses at an extremely fast rate, and the baby has powers that allow it to communicate with Bella and Edward telepathically even before it's born. This causes them to reevaluate their relationship and what they thought they knew about vampires and half - vampire children.
Well, a possible plot twist is that after the car crash, Bella's blood has some strange reaction that makes her immune to vampire bites. So, Edward is both relieved and worried as this changes their relationship dynamic. Also, the car crash could lead to a time - travel situation where Bella goes back in time to prevent the crash from ever happening. Or, it could be that the car crash causes Edward to lose some of his vampire powers temporarily, and he has to rely on Bella and human methods to survive while they figure out how to get his powers back.
One interesting plot twist could be that Bella realizes she doesn't want either of them and decides to go off on her own journey of self - discovery. This would completely change the dynamic of the love triangle.
One possible plot twist could be that the twins have some sort of special power. Maybe they can communicate telepathically from the womb, which causes Bella to have strange visions and Edward to sense something unusual even though he's left. Another could be that Bella discovers a hidden family secret about her own lineage that is related to the twins and their potential abilities. This could lead her on a journey of self - discovery while dealing with the pregnancy alone.
One interesting plot twist could be that Bella discovers a new power that is completely unexpected. For example, she might be able to control the elements in some fanfiction stories. This would add a whole new layer to her character and the story.
In some fanfictions, their marriage might lead to the discovery of new powers. For example, Bella's unique human - turned - vampire nature combined with Edward's abilities could result in a special power that helps them protect their family. It could be something like a telepathic bond that is even more powerful than Edward's existing one.
In some Edward and Bella marriage fanfiction, there could be a plotline where they face threats from other vampire clans who are not happy about their union. This would lead to a lot of action and drama, with Edward and Bella having to fight to protect their marriage and their family. They might have to rely on their friends and allies within the vampire and human worlds to overcome these challenges.
Another possibility is that Edward betrays Bella by revealing her secrets to their enemies. Maybe he was forced to do so under some sort of blackmail from a powerful and malicious vampire or other supernatural being. In this case, Bella would have to face the consequences of having her secrets exposed while also dealing with Edward's betrayal.
One possible plotline could be Bella initially resenting the forced marriage but gradually discovers Edward's hidden kindness and they start to fall in love for real. For example, Edward might go out of his way to protect Bella from the threats in their supernatural world, which makes Bella see him in a new light.