Perhaps in the fanfiction, Stefan marries Elena and Caroline in a parallel universe where the rules of love and relationships are different. Stefan realizes that he has deep feelings for both of them and decides to marry them in a grand ceremony. This leads to a series of adventures as they try to merge their different worlds and deal with the jealousy and insecurities that come up among the three of them.
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.
Perhaps in the fanfiction, they go on a honeymoon to a place that has significance to both of them in their past. It could be a place where they first met as vampires or a place that was important in their human lives. Along the way, they encounter other supernatural beings that test their relationship. But their bond as a married couple is strong enough to overcome these obstacles.
Another theme is the development of characters' emotions over time. As Stefan navigates his love for the two, we see how Elena and Caroline also grow and change in their relationships with him and with each other. For example, in some fanfictions, they might start off as rivals but end up as friends who understand each other's connection to Stefan.
One possibility is that Stefan is under some dark spell or influenced by an evil force. Maybe he kidnaps Elena to protect her from a greater danger that he believes only he can handle, but his actions are misinterpreted. For example, there could be a new vampire hunter in town who has a special weapon that can kill vampires instantly, and Stefan thinks the only way to keep Elena safe is to take her to a hidden location.
Well, perhaps the plot could revolve around the challenges they face as new parents. Maybe they struggle to balance their supernatural lives with raising a child. For example, they have to protect the baby from the various threats in their world like other vampires or werewolves who might see the baby as a target or a powerful asset. They could also have cute family moments, like Stefan teaching the baby to walk while Caroline reads bedtime stories filled with their own adventures in a vampiric world.
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.
Well, 'Stefan's Dual Affections' is a great one too. It focuses on Stefan's internal struggle between his love for Elena, which is more of a traditional, deep-rooted love, and his growing feelings for Caroline, which are filled with a sense of new discovery and excitement.
You can find such fanfiction on FanFiction.net. It has a large collection of fan - created stories related to various shows and characters, including those centered around Stefan, Elena, and Caroline.
Damon might initially be shocked and angry. He has always had feelings for Elena, and seeing Stefan marry both her and Caroline could make him feel betrayed. He might lash out and try to cause trouble for their relationship at first.
Another plot could involve Caroline's werewolf friend Tyler coming back and being initially skeptical but then becoming a strong support for them during the pregnancy. This could add some drama as there are historical tensions between vampires and werewolves.