One possible plot could be that the twin has been hidden away by some dark force all this time. When Harry discovers the twin, they have to figure out how to break the spell or curse that was placed on the twin. Another plot might be that the twin has been living in the Muggle world, unaware of their magical heritage, and Harry has to introduce them to the wizarding world and they face various challenges together.
Well, it depends on the specific fan fiction. Sometimes, Harry finding out he has mates can lead to a polyamorous relationship which is quite different from the traditional relationships in the original Harry Potter series. This can be really interesting as it shows how fan fiction can take the existing characters and put them in unique situations that the original author might not have considered. It can also be a way to explore themes of love, acceptance, and self - discovery for Harry.
Often, there are plots centered around secrecy. Harry might worry about how others will react, like his friends Hermione and Ron. So, he tries to keep his relationship with his mates a secret. And then there's the plot of the mates themselves getting to know each other better. Since they are all in a relationship with Harry, they need to form their own bonds too, which can lead to some really interesting interactions and storylines.
One popular one could be 'The Unforeseen Bond'. In this fan fiction, Harry discovers his mate in the most unexpected of places, like during a Quidditch match when he feels an instant connection to a new student. It has a really engaging plot with a lot of sweet moments between Harry and his mate as they navigate their new relationship while also dealing with the usual Hogwarts chaos.
Maybe Harry discovers he was secretly adopted by the Weasleys all along. So he has to adjust to this new reality and learn about his true family ties within the Weasley clan.
Severus might be initially shocked. He could feel a strange sense of protectiveness over Harry, despite their past differences. He might try to find out who wrote the fan fiction and why they depicted such a disturbing scenario.
In this fan fiction, Harry might initially deny the whole thing. But as he starts to explore this new side of himself, he could discover some hidden secrets about the Malfoy family. This could change his perception of the Malfoys completely. And who knows, it might even lead to a new form of magic or power that he has access to because of his newfound 'Malfoy - ness'.
It could be the person who stole Harry in the first place. Maybe they are a powerful wizard who wants to keep Harry away from his real family for some self - serving reasons. They might be afraid that if Harry reunites with his true family, they will lose some kind of power or influence they have gained from keeping Harry in the dark.
Obviously, Harry Potter himself as he is the one finding out this huge truth. And the Weasley family members, especially those like Mr. and Mrs. Weasley who would play important roles in helping Harry understand his new identity.
Well, Harry Potter is the main character as the story revolves around his discovery. Draco Malfoy is crucial as it's a 'Malfoy Romance' story. There could also be new characters introduced that are related to the Malfoy family's secrets. Ginny Weasley might also be in the picture, perhaps being jealous or trying to understand Harry's new connection. And don't forget about Dumbledore, who might have known something all along and could offer some guidance to Harry in this strange new situation.