A really interesting plotline could be that the secret child is being targeted by an old enemy of Harry's. Maybe Voldemort's remaining followers see the child as a way to get revenge on Harry. So, Harry has to protect the child while also dealing with the fact that he's been keeping this big secret from everyone he loves. It would show his growth as a character as he tries to balance his new role as a father with his existing responsibilities in the wizarding world.
One possible plotline could be the discovery of the secret child and how it affects Harry's relationships with his friends and family. For example, Hermione and Ron might be shocked at first but then become supportive. Another could be the challenges the child faces growing up in the wizarding world with this secret hanging over them.
In some 'Harry and Draco secret child fanfiction', there could be a plotline where the child serves as a bridge between the two families. Harry's side, like the Weasleys, and Draco's family might initially be against the idea of the child. But as the story progresses, the child's presence changes their perspectives. The child might also struggle with its own identity, being part wizard from two very different backgrounds, and this internal struggle could be a central part of the story.
Perhaps a plotline where Harry discovers other immortal beings. He could form a sort of community with them, learning about different cultures and powers that immortality has bestowed upon them. They might teach him how to better control his immortality, like hiding his true nature from mortals or using his extended lifespan to gain knowledge that no one else has. This could lead to adventures as they try to protect their secret from those who would seek to exploit it.
In some Harry and Ginny Cursed Child fanfictions, the plot could revolve around their children. Ginny might notice some strange behavior in their kids that she suspects is related to the Cursed Child's influence. She then teams up with Harry to investigate. They could find out that there are some latent magical powers in their children that are being affected by the dark magic from the Cursed Child's events. This could lead to a series of challenges and adventures as they try to help their children and safeguard the wizarding world.
Well, perhaps the child in the 'Harry Potter child in Azkaban' fanfiction forms unexpected alliances. Maybe they team up with some of the inmates who have their own reasons to oppose the unjust system of Azkaban. This could lead to a series of adventures where they try to break free from Azkaban's clutches together.
One possible interesting plotline could be the Rose Child having unique magical abilities that are different from the regular magic in the Harry Potter world. For example, they might be able to communicate with a special kind of magical creature that others can't.
Another plotline might involve Harry making new friends at the secret school who have different backgrounds and powers. They could team up to solve a mystery within the school, like a series of strange disappearances or a hidden treasure.
Well, a plotline might involve Tonks using her Metamorphmagus abilities to secretly meet Harry in different disguises. This adds an element of mystery and fun to their relationship. They could also be sharing secrets about their past traumas, like Harry's experiences with Voldemort and Tonks' insecurities, which deepens their bond on a more emotional level. Maybe there's a sub - plot where they have to keep their relationship from Tonks' family, especially her Auror colleagues who might not approve.
One interesting plotline could be them secretly helping each other with schoolwork. Harry, with his practical knowledge from his adventures, and Daphne, with her in - depth understanding of pure - blood magic. They might exchange tips and spells in a hidden corner of the library.
Another plotline could involve the baby having some sort of special power. This would add an element of mystery and adventure as they try to protect the baby from those who might want to use its power for evil.
One interesting idea could be the exploration of how the secret child discovers their magical heritage. For example, they might start showing accidental magic and then begin to piece together their connection to Harry Potter. Another idea could be the child facing unique challenges in the wizarding world that are different from what Harry faced, like dealing with the expectations of being Harry's child in a more modern and changed wizarding society.