One idea could be that they discover a shared power that only they can control together. They initially struggle with their relationship due to the taboo nature of it, but as they learn more about this power, they start to see each other in a new light and form a strong bond.
Perhaps in the fanfiction, they are forced to team up to face a common enemy. Their half - brother has some knowledge or skills that Hope needs, and vice versa. Along the way, they have to deal with the judgment of their family and friends, but they gradually realize that their connection is deeper than just being half - siblings.
One idea could be that Hope, being a powerful witch herself, is sent to Hogwarts on an exchange program. There, she meets Harry Potter and they bond over their shared experiences of being different from their peers. Another plot could involve a dark magic threat that only their combined powers can defeat. They start as strangers, but as they train together, they develop a deep friendship and mutual respect.
Well, a plot could revolve around Hope having visions of Klaus's future. In these visions, she sees that he's in great danger from an ancient evil that is about to be unleashed. So, she sets out on a journey to find a way to prevent this from happening. Along the way, they have to face their own personal demons as well. Maybe Hope has to come to terms with her anger towards Klaus for not being there for her all the time. Another plot could be that Klaus is cursed and Hope is the only one who can break the curse, but it comes at a great cost to her powers.
One idea could be a crossover where Percy and Hope team up to fight a common enemy that threatens both the demigod and the supernatural worlds. Maybe an ancient evil that has the power to disrupt the balance between the gods and the vampires/werewolves/etc.
One idea could be that Hope Mikaelson, with her powerful witch abilities, is somehow transported to the Marvel universe. She could end up at the X - Men's school and learn new ways to control her powers from Professor Xavier. Another plot could involve her teaming up with Scarlet Witch. Since they both have strong magic, they could face a common enemy like a powerful dark magic - based villain who is threatening both the Vampire Diaries - related world and the Marvel world.
One idea could be that Hope, with her unique powers as a Mikaelson, visits Hogwarts for a special exchange program. She could end up befriending Harry and together they face a new dark threat that combines the magic of the wizarding world and the supernatural powers of the Mikaelsons. Maybe a dark wizard is trying to harness the power of the Mikaelson bloodline for some evil spell, and Harry and Hope must stop it.
One idea could be that Hope discovers she's pregnant during a time of great turmoil in the supernatural world. She has to hide her pregnancy to protect her unborn child from those who might want to use it for their own gain. Maybe she goes into hiding with a trusted friend or family member.
Perhaps Naruto's half - brother was raised in a different village by an enemy of Konoha. He initially hates Naruto but as he gets to know the real Naruto and the values of Konoha, he has a change of heart. They could team up to stop a conspiracy that threatens both their villages. He might also have some special skills in espionage which he uses to their advantage.
One idea could be the human sister getting caught in the middle of a vampire - werewolf feud because of her relation to Hope. Maybe she tries to broker peace between the two factions using her unique position as a human in a supernatural - filled world.
One idea could be a crossover with the Vampire Diaries. Hope could meet Elena and they could form an unlikely alliance against a new threat in Mystic Falls. Maybe a powerful witch from another dimension is causing chaos and their combined powers are needed to stop it.
Perhaps there could be a situation where a dark magic spell in the Potter universe somehow links to the Original vampire's curse in Klaus's world. Harry and Klaus are forced to work together to break the spell/curse. Along the way, Klaus sees a bit of himself in Harry's determination and Harry realizes that Klaus isn't entirely a monster.