Klaus is often the most complex. He has a long and troubled past filled with violence and betrayal. In fanfiction, his feelings for Caroline and Camille can be very conflicted. He loves Caroline but also has a connection with Camille. His inner struggle between his dark nature and his love for these two very different women makes him a complex character to write about.
I think Caroline can also be very complex. She is a strong - willed vampire with her own set of values. In the context of this fanfiction, she has to deal with Klaus's past and his connection with Camille. She may have insecurities about her relationship with Klaus, especially when Camille is in the picture. Her growth and how she handles these complex emotions add to her complexity.
One idea could be that Klaus and Caroline are in a relationship, but Camille's presence causes some jealousy and tension. For example, Camille might still have some unresolved feelings for Klaus, and Caroline has to deal with that while also trying to strengthen her bond with Klaus.
Caroline as a human in fanfiction with Klaus can create a really interesting dynamic. It allows for exploration of how a human might interact with a powerful vampire like Klaus. For example, she could be a source of light in his dark world, constantly challenging his views.
Stefan could also play a role. Since he and Caroline are friends and he has a history with Klaus, he might step in to try and stop the marriage. He could try to negotiate with Klaus or find some other way to free Caroline.
There's also 'The Unlikely Bond'. This fanfiction delves deep into how Caroline and Klaus might interact outside of the main plot of the show. It shows their different personalities clashing and then gradually coming together in a really engaging way. It's full of great dialogue and some really sweet moments between them.
Klaus shows his love by protecting Caroline. He would always be there to save her from any danger, whether it's from other vampires or supernatural threats.
Klaus would be very attentive to Caroline's pregnancy cravings. He'd see it as his duty to take care of her during this time. He might cook for her himself if he can, or take her to the best restaurants to get what she wants. He would be a bit overprotective too, making sure that whatever she eats is of the highest quality and safe for her and the baby. He'd also listen intently to her when she talks about her cravings, finding it endearing and a sign of the new life growing inside her.
Klaus might be overjoyed. He has always been attracted to Caroline, and having a baby with her could be the ultimate sign of their connection. He would probably be very protective, using all his power and resources to keep her and the unborn baby safe.
Their relationship could become more intimate as they bond over the baby. They might start to see each other in a new light, with Klaus showing a more tender side and Caroline learning to trust him more deeply.
It could become more intense. They now have a shared responsibility, so they might be more connected. Klaus might be more tender towards Caroline, and Caroline might start to see Klaus in a different light, perhaps more as a partner rather than just an acquaintance.
One popular theme is redemption. Fans like to see Klaus find redemption through his relationship with Caroline. It gives his character a chance to grow and change for the better.