Another possibility is that Shego is being controlled or influenced by some external force. This external entity might have a vendetta against Kim and is using Shego as a tool to carry out the killing. Shego, being in a subservient position to this force, has no choice but to try and kill Kim.
One consequence could be a power vacuum. If Kim was in a position of power or influence, her death would leave a void that other characters would scramble to fill. This could lead to chaos as different characters fight for her position.
One possible scenario in a Shego and Kim fanfic could be that they are forced to team up against a common enemy. Maybe a new villain emerges who has a power that can only be countered by the combined skills of Shego and Kim. They start off hesitant to work together, but as they face challenges, they begin to respect each other's abilities more.
One common theme is the exploration of their relationship, whether it's adversarial or evolving into something more friendly. Another theme is Shego's own self - discovery, as she often has a complex backstory in fanfiction. Also, the power dynamic between them, with Kim being the hero and Shego the villain, is frequently explored.
The setting can also be important. Placing them in a different world or time period, like a steampunk version of their world or in an ancient civilization, can add a whole new layer of interest to the story. This allows for creative interpretations of their characters and how they would interact in such settings.
Another theme is friendship or the potential for it. Despite their differences, many fanfics show Kim and Shego developing a bond that goes beyond their initial enmity. This can involve themes of loyalty and understanding.
Their relationship would become much more complex. They would have to put aside their differences and work together for the sake of the baby. Instead of being just enemies, they would become reluctant partners in parenting.
The main characters are Kim and Shego, of course. Kim is usually portrayed as a brave and determined hero, while Shego is often her nemesis, with her own set of powers and a rather sassy attitude.
Shego and Kim as unlikely allies could mean that they are brought together by fate. Perhaps a powerful artifact is about to be misused, and they are the only two who know how to stop it. Their initial meetings would be full of tension, but as they start to understand each other's motives, they form a tentative bond.
In a Shego - kidnaps - Kim - Possible fanfiction, the plot could be filled with high - stakes action. Shego might have some devious plan behind the kidnapping, perhaps related to a powerful artifact Kim was about to retrieve. Kim, being the resourceful hero, would surely find ways to outwit Shego even in captivity. This could lead to an exciting cat - and - mouse game within the story.
I'm not very familiar with this particular adult fiction titled 'Shego Marries Kim'. It might be a relatively unknown piece in the vast world of adult fiction. Maybe it has a small but dedicated following within certain circles.