Yes, there are likely some out there. Fanfiction is a vast world, and many creative fans come up with all sorts of unique family relationships in their stories. You can try searching on popular fanfiction websites like Archive of Our Own or Fanfiction.net. Just type in 'Harry is Klaus son' in the search bar and see what pops up.
One possible plot could be that Harry discovers his true heritage as Klaus' son. This could lead to a whole new set of powers and abilities for him, as well as a new family dynamic. Maybe he has to navigate the vampire world while still dealing with his wizarding roots. He could face challenges from both the wizarding community who are suspicious of his newfound vampire side, and the vampire world which might not fully accept him because of his wizard heritage.
Well, perhaps it could be about Harry Potter having to deal with the dark and complex nature of Klaus within him. Maybe he discovers new magical abilities that come from his 'father' Klaus, and he has to struggle to control them while still being the hero we know from the original Potter stories.
Yes. In fanfiction, writers love to blend different fictional worlds and create unique scenarios. If Harry Potter was Klaus Mikaelson's son in a fanfic, it would bring about a whole new set of storylines. For example, how would Hogwarts react to a student with not only magic but also a vampire - werewolf heritage? How would Dumbledore deal with a student who has the complex and often dark nature of Klaus? And how would Harry's relationships with his friends, like Ron and Hermione, change in this new context?
The characters would interact in very interesting ways. For example, Dumbledore might be more cautious around Harry, as he's the son of Klaus. He would probably keep a closer eye on him to make sure he doesn't turn to the dark side. Harry's friends, on the other hand, would be both curious and a bit worried. They would still support him but also question some of his actions if they seem too much like Klaus's.
Maybe Harry discovers his Mikaelson heritage when strange things start to happen to him during his time at Hogwarts. His newfound powers could attract the attention of both the wizarding world and the supernatural world from Klaus' side, leading to a complex web of alliances and rivalries. He might have to learn how to balance his wizarding skills with his vampire - like abilities.
In such a fanfiction, the plot could involve Harry being hidden from Klaus's enemies in the wizarding world. As he grows up, he discovers his true parentage through some magical or supernatural means. His connection to Klaus might give him unique powers, like enhanced strength and speed along with his magic. He could be caught in a war between the magical community that wants to keep the vampire - werewolf world at bay and Klaus's allies who want to bring Harry into their fold. Harry has to decide which side he truly belongs to and fight for what he believes in, all while trying to understand his complex heritage.
Harry would likely be more ruthless. Klaus has a reputation for being cruel when necessary, and Harry might have a bit of that in him. He may not hesitate as much to use more extreme measures against his enemies, like the Death Eaters. However, he would also have to struggle with this darker side of his nature, as he has been brought up in the relatively more morally - bound wizarding world. His friends like Hermione and Ron might be shocked at first by these new aspects of his personality, but they would also try to help him stay true to the good values he has learned at Hogwarts.
Yes, there are quite a few. You can start by looking on fanfiction websites like Archive of Our Own. There you might find some interesting stories exploring the relationship between Harry and Klaus as mates.
One common theme is the power dynamic. Since both Harry and Klaus are powerful in their own rights, how they balance that power as mates is often explored.