They could develop a shared hobby. For instance, they both get into painting and use it as a way to express their emotions and connect on a deeper level. It would be unique because it shows a side of them that's not related to their supernatural natures.
In many 'The Vampire Diaries' Kol and Elena fanfictions, their relationship can be quite complex. Kol is often depicted as a wildcard, and his interactions with Elena can range from intense and dangerous to oddly alluring. Some fanfictions might explore a forbidden - love - type scenario, where Kol's vampiric nature and his family's history with Elena's friends create barriers. However, they also might find common ground in their mutual experiences of being caught up in the supernatural chaos of Mystic Falls.
The other vampire clans might be antagonists. They could see the baby as a threat to the vampire hierarchy or fear that the baby will have powers that could disrupt the balance among vampires. For example, the Originals' siblings who don't trust Kol might try to stop Elena from having the baby.
One possible plot could be that Kol kidnaps Elena to use her as bait for his enemies. He might think that by having Elena in his custody, her friends, especially the Salvatores, would come to rescue her and he could then ambush them. Another idea is that Kol has some sort of vendetta against Elena because of her connection to the doppelganger bloodline. So he kidnaps her to extract revenge on the entire line.
One common theme is forbidden love. Since Kol and Elena might be from different 'worlds' or groups within the show's lore, their relationship can be seen as something that goes against the norm. Another theme could be passion. The kiss is often a moment of intense passion that drives the story forward.
Another character that could be important is Elijah. He is often the voice of reason among the Originals. He might try to guide Kol in his relationship with Elena, or he could be against it if he thinks it will bring trouble to their family. So in this fanfiction, he could be a key figure in the development of the Kol - Elena relationship.
The plot might involve Kol falling in love with Elena. Kol, being the wildcard among the Originals, could try to win Elena over in his own unique way, which might create a lot of drama with the other characters like Damon and Stefan who are also interested in Elena.
I really liked a fanfic where Elena and Kol time travel to the Middle Ages. It's a bit of a different take as they have to navigate the social norms of that time while also dealing with their own feelings. There are some really intense and romantic scenes in it. It shows how their characters develop in a new and challenging environment.
One popular 'kol and elena fanfiction' might be those that explore their relationship in an alternate universe where they are on a journey together to discover a hidden magic. In these stories, Kol could be protecting Elena from various threats, adding an element of adventure.
The relationship would shock Damon and Stefan. They have always been protective of Elena, and Kol has a reputation as a dangerous vampire. Damon might be especially angry and try to drive Kol away from Elena. Bonnie would also be concerned as she has seen Kol's past actions. However, Caroline might be more open - minded and could potentially try to help Elena understand her feelings for Kol. Klaus would be an interesting factor too. He might see Kol's relationship with Elena as a way to gain an advantage in his power games or he could be protective of his brother's new - found love.