Well, they could start a new life away from all the chaos. They find a peaceful place where no one knows them and try to raise their baby in secrecy. But then, their past catches up with them. Maybe an old enemy of Kol's discovers their location. Another angle is that the baby has some unique powers even before birth, and this attracts the attention of both good and bad elements in the supernatural world. Bonnie and Kol then have to figure out how to handle this situation without putting their baby in danger.
In a fanfiction plot, Bonnie being pregnant could lead to a story where she forms an unexpected alliance. For instance, she might team up with a heretofore enemy because they have some knowledge about how to keep the baby safe during her pregnancy. Also, the pregnancy could be a sign of a prophecy in the Vampire Diaries universe. This could set Bonnie on a journey to figure out what the prophecy means for her baby and the future of Mystic Falls.
A plot could involve Elena and Kol having to deal with an ancient prophecy related to their unborn child. They have to figure out what it means and how to prevent any negative consequences. Along the way, they learn more about each other's pasts and how their families' histories are intertwined with this prophecy, which makes them more determined to protect their family.
One idea could be that Bonnie discovers she's pregnant during a time of great chaos in the magical world. She has to keep it a secret while trying to protect herself and her unborn child from dark forces. Another could be a story where the father of the baby is a mystery, and Bonnie goes on a journey to figure it out all while dealing with the physical and emotional changes of pregnancy.
One idea could be that Bonnie discovers she's pregnant during a time of great turmoil in the supernatural world. She and Stefan then have to figure out how to protect their unborn child from all the threats. Maybe they go into hiding, and along the way, they face challenges that test their relationship and their will to survive.
One idea could be exploring how the other characters in the FNAF universe react to Bonnie's pregnancy. They might be confused, excited, or worried. Another could be the challenges Bonnie faces during the pregnancy, like dealing with her animatronic body limitations.
A possible plot is that they travel back to a time when the Original family was first created. Kol could introduce Bonnie to his family, which would be a very interesting encounter. Bonnie might use her magic to help or hinder the family's early days, depending on how she feels about them. Or perhaps they time travel to a key moment in Bonnie's family history, like when her powers were first discovered in her family line. Kol could be there to support her as she discovers more about her roots and the origin of her power.
One possible storyline could be the challenges they face as a couple expecting a child in a world full of supernatural threats. For example, they might have to protect their unborn baby from other vampires or witches who see it as a threat or a powerful tool. Another idea is that the pregnancy could bring out a different side of Kol, making him more protective and less impulsive. And Bonnie could struggle with her magic during pregnancy, fearing it might harm the baby.
One idea could be that Kol and Elena are in a forbidden love situation. Maybe in a world where the supernatural factions are at odds, and their relationship is seen as a threat to the balance. Another could be a time - travel plot where Elena goes back in time and meets a younger Kol, changing the course of their relationship.
Perhaps the fanfiction could explore the challenges they face due to their different natures. Elijah being a vampire and Bonnie being a witch. There could be concerns about the health of the baby, with Bonnie using her magic to ensure a safe pregnancy and Elijah struggling with his vampiric instincts, like the urge to drink blood while being around his pregnant partner.
One idea could be exploring how Yennefer deals with the physical and emotional changes during pregnancy while still being a powerful sorceress. Maybe she has to find a way to protect her unborn child from the many enemies she has made.