Another plot could be that the baby has some unique supernatural abilities that neither Stefan nor Elena expected. This could lead to them having to search for answers about the baby's powers. They might seek help from their friends like Caroline and Damon. Along the way, they encounter various characters who either want to help or harm the baby because of its special nature.
They would become more protective of each other. Stefan, being the protective vampire, would be constantly on guard to keep Elena and the unborn baby safe. Elena, on the other hand, would be more nurturing towards Stefan, seeing him as the father of her child.
In such a fanfiction, perhaps the plot could involve a lot of drama. Stefan might initially be in shock at the unexpected pregnancies. There could be a rift between him and his friends due to the complex situation. He would have to figure out how to support both Elena and Caroline during their pregnancies, and also deal with the reactions of the Mystic Falls community. Maybe he would start to realize his deeper feelings for both of them as they go through this life - changing experience together.
Elena would likely be angry. She has her own agency and doesn't like being controlled. If Stefan kidnapped her, she would fight back. She might use her knowledge of the supernatural world and her relationships with other characters to try to escape. For example, she could try to call out to Damon telepathically if they have some sort of connection in the story.
Caroline would probably be overjoyed and very helpful. She might offer to babysit all the time and give parenting advice based on her own experiences or what she's read. Damon, on the other hand, might be a bit more cynical at first, but eventually grow to love the baby and become very protective.
Well, Stefan's relationship with Elena and Caroline would transform into something more family - oriented. They would have to rely on each other more than ever. There could be a lot of emotional moments as they navigate this new chapter. Elena and Caroline's relationship could evolve from just being friends to co - parents - in - a - way with Stefan. And Stefan would have to deal with the fact that his actions have not only affected his own relationships but also the dynamics within the whole group of friends in Mystic Falls.
One idea could be that they struggle with how to tell their friends and family. Since their relationship has had so many twists and turns, they're worried about the reactions. Another could be that they face some kind of supernatural threat to the pregnancy, which adds a lot of drama and action to the story.
I'm sorry, I haven't read this specific fanfiction. But you can try to find it on popular fanfiction websites like Archive of Our Own or Fanfiction.net.
One common theme is the idea of eternal love. Since they are in a supernatural world, their love is often depicted as something that can transcend time and death. For example, in many fanfictions, even if one of them is in danger or seemingly lost, their love remains unwavering.
Caroline, for example, might be more accepting as she is also a vampire. She could help Elena adjust to her new life. Damon, on the other hand, might be jealous or feel threatened that Stefan made Elena a vampire. It could change the power balance between the three of them.