A sense of identity is a big theme as well. Growing up as Klaus's daughter, she has to figure out who she is on her own. Is she just defined by her father? Or does she create her own identity? These are the kinds of questions that are often explored in this type of fanfiction, which makes it really engaging for readers who are interested in character - driven stories.
One common theme is identity crisis. Harry, being Klaus's daughter, has to figure out who she really is in relation to both her wizarding past and her new vampire heritage. Another theme is family drama. Since Klaus has a complex family history in the Vampire Diaries universe, Harry gets caught up in all that drama.
Well, a very common theme is the exploration of heritage. Bella, who was an ordinary girl in the 'Twilight' world (sort of), now has to understand her new vampire - hybrid heritage as Klaus's daughter. There's also the theme of loyalty. She has to decide where her loyalties lie, between her old friends and family in Forks and her newfound family in Klaus's world. And of course, love. How does her new identity affect her relationships, especially with Edward or any other love interests she had in the 'Twilight' series? All these themes are often explored in such fanfictions.
Yes, there are quite a few. In many of these fanfictions, the idea of Bella being Klaus's daughter brings a whole new dynamic to the story. It often involves a mix of the 'Twilight' and 'The Vampire Diaries' universes, as Klaus is from 'The Vampire Diaries' and Bella is from 'Twilight'. Writers usually play with the idea of combining the different mythologies and powers from both series. For example, Bella might inherit some of Klaus's unique vampire abilities, which then changes the way she interacts with the other characters in her 'Twilight' world.
There's 'Forgotten No More'. In this fanfiction, the forgotten daughter has unique powers that set her apart. As she enters the Mikaelson world, she faces both acceptance and rejection from different family members. It shows how she overcomes the challenges of being an outsider in her own family and forges her own path, with Klaus having a particularly difficult time coming to terms with her existence at first.
They're popular because they add a new dimension to the already rich Vampire Diaries and The Originals universe. People love exploring the idea of a hidden family member and the drama that comes with it.
One common theme is the struggle for acceptance. The OC daughter often has to deal with Klaus's complex personality and the whole vampire - werewolf - witch world she's born into. Another theme is family loyalty. Despite the challenges, she usually shows great loyalty to Klaus and the rest of the Mikaelson family.
There are often 'klaus daughter oc fanfiction' that involve her getting involved in the family drama. She could be a mediator between Klaus and his siblings, trying to bring peace to the family. In these stories, the daughter's character development is usually the key point, as she grows and learns more about her family's complex history.
She is sometimes shown as a very strong - willed individual. Since she is human in a family of vampires and other supernatural creatures, she has to be tough. Fanfictions may portray her as using her wits to survive. Maybe she becomes friends with some of the other characters in Klaus' world who help protect her. For instance, she could form a bond with Elijah, Klaus' brother, who sees her as a symbol of hope for Klaus to become more human - like in his actions and emotions.
I'm not sure about a lot of specific 'harry is klaus daughter fanfiction' but you can try searching on fanfiction.net or Archive of Our Own. Just type in the keywords 'harry is klaus daughter' and you'll likely find a bunch. Some might explore how Harry's magical abilities from the Harry Potter world interact with the supernatural elements of being Klaus's daughter in the Vampire Diaries universe.