There should not be any such fanfic. The Harry Potter series is about friendship, courage and magic, not about abuse. This kind of concept goes against the positive values that the original work promotes. It is also unethical and can be very disturbing to the fans who love the original story.
One interesting 'Harry Potter little sister' fanfic could be where she has a unique magical ability that Harry doesn't have. For example, she might be able to communicate with magical creatures in a way no one else can. This could lead to all sorts of adventures, like helping Hagrid with some of his more dangerous beast - handling tasks.
One common theme is family. Since it's about Harry having a little sister, it often explores the family dynamic. How they support each other, protect one another, and sometimes even have sibling rivalries. Another theme is identity. The little sister has to figure out who she is in the shadow of her famous brother.
A squib in the Harry Potter universe is a person born into a magical family but lacks the ability to perform magic. In a 'no magic' fanfic, it could be really interesting to explore how a squib might navigate the wizarding world. They might face discrimination or be overlooked. They could also find unique ways to contribute, like being really good at understanding magical artifacts even without being able to use them.
No. Writing 'smut' (pornographic or sexually explicit) fanfic involving characters from the Harry Potter series is inappropriate. The Harry Potter franchise is aimed at a wide audience including children and young adults, and such content goes against the family - friendly and magical essence of the original work.
Good 'Harry Potter Little Harry Fanfic' often focuses on Harry's innocence and his discovery of the wizarding world. It should capture the magic and wonder that a young child would experience. For example, it might show how he reacts to seeing his first magical creature or receiving his first wand.
The fanfic could center around Harry's life outside of the main events of the books. For example, it could explore his summer holidays in more detail. He could be spending time in the Muggle world and using his magic in creative ways to solve normal, everyday problems. He might use magic to help his neighbor fix a broken fence without the neighbor realizing it was magic. This would add a new dimension to his character and show how he can adapt his magical abilities to different situations.
Ron and Hermione are likely to interact with them. Ron might be a bit more protective of the sister, while Hermione would probably study and share knowledge with her. They could all be in the Gryffindor common room, discussing spells and strategies.
It changes the family dynamic. Instead of being an only child, Harry now has a sister, which means there's more family support or potential family drama. For instance, the sister could be a target of Voldemort too, adding another layer of danger.
No. The original Harry Potter series is mainly aimed at a wide range of audiences including children and young adults. It has a huge following because of its themes of friendship, courage, and magic. The story is more about the growth of the characters in a magical world, not what this statement implies.