A plotline could involve them discovering new magical abilities or powers as a result of this trauma. It's possible that the emotional upheaval of being disowned unlocks latent magic within them. They could then use these new powers to not only better their own situation but also to help other outcasts in the wizarding world. Maybe they start a secret group for those who have been rejected by their families.
One plotline could be Harry finding a new family among his friends at Hogwarts. They become his support system and help him grow in ways his biological parents couldn't. Another could be Harry's journey to discover why his parents disowned him and uncovering some dark family secret along the way.
Perhaps Harry is disowned because his parents believe he has been corrupted by dark magic. So he has to prove his innocence and find a way to reverse their decision. Along the way, he meets a mentor who helps him master his magic in a new and unique way, different from what he would have learned from his parents.
One possible plotline could be Harry feeling extremely lost and alone at first. He might have to find a new place to live, perhaps with the help of his friends like Ron and Hermione. He could struggle with self - worth, constantly wondering what he did wrong to make his parents disown him.
A third plotline could revolve around a magical object or a special power that only Harry seems to have access to. For example, if there was a new magical amulet discovered that has a special connection with Harry. Hermione, being the knowledge - thirsty witch she is, might be jealous that Harry gets to experience and explore the powers of this amulet while she is left out. This could lead to a rift in their friendship until they figure out how to share or include Hermione in the discovery.
A plotline could involve Naruto being disowned and then finding out that his parents were actually being controlled by an enemy. He then has to decide whether to forgive them or not while also dealing with the new threat. Or perhaps Naruto is disowned and he starts to form his own ninja group of outcasts, fighting against the traditional ninja villages that shunned him. This could lead to a whole new set of power dynamics and battles.
She might throw herself into her studies even more. Since she has always been studious, she could use her academic pursuits as a way to distract herself from the pain of being disowned. She may also lean more on her friends in the wizarding world, like Harry and Ron, for emotional support.
One possible plotline could be Harry finding new and unexpected allies outside of the wizarding world he once knew. Maybe he discovers a hidden community of magical beings who are shunned by the mainstream wizarding society and they take him in.
They could have been disowned if they took a stance on a political or magical issue that was against their parents' beliefs. For instance, if there was a conflict between pure - blood and half - blood wizards, and Harry and Ginny sided with the half - bloods when their pure - blood parents were firmly against it. This difference in ideology could cause a rift so large that their parents would disown them.
A third plotline might be that Harry is abandoned in a magical but hidden place. There, he is raised by magical creatures, say, a group of centaurs. They teach him their own brand of magic and wisdom. When he finally enters the wizarding world proper, he has a very different perspective on magic compared to the other students, which causes both admiration and some envy among his peers.
A plotline could be that Harry, after being dumped by his parents, has a very different personality. He's more withdrawn and distrustful. Sirius has to work hard to break through those walls. They could travel to different magical places to find a way to reverse what Harry's parents did or to find out the real reason behind it. Along the way, they meet other characters who either help or hinder their journey, and this all shapes their relationship and Harry's growth as a person.