The Greengrass sisters, like Daphne and Astoria Greengrass, are likely to be main characters as well. Their interactions with Harry would be a central part of the story. For example, Daphne might be initially suspicious of Harry but then grow to respect and befriend him.
Obviously, Harry Potter is one of the main characters. He is the one who is living with the Greengrass family.
There could also be other Hogwarts students who are related to the plot involving Harry and the Greengrass family. For example, Hermione and Ron might be involved as Harry's friends. They could be either supportive or skeptical of Harry's newfound connection to the Greengrass family.
Dumbledore could also be a major character. As the headmaster of Hogwarts, he has a big influence on Harry's life at the school. And maybe some of the Hogwarts ghosts like Nearly Headless Nick would play significant roles in the story as well.
Obviously, Harry Potter is one of the main characters. He is the boy who lived and has his own story filled with battles against Voldemort. Nicolas Flamel is another main character. He is an ancient and very powerful alchemist who created the Philosopher's Stone.
At first, it might be a bit tense. The Greengrass family is a pure - blood family, and Harry is an orphan with a strange past. But as they get to know each other, they could develop a mutual respect. Harry might show them that blood status doesn't matter, and they could teach Harry about their family's magic heritage.
In the fanfiction world, Greengrass is often a Slytherin student. She usually comes from a pure - blood family, which gives her certain status and expectations within the wizarding world. In the context of rescuing Harry Potter, she might be a character with a strong sense of justice that goes against the typical Slytherin stereotype. She could have her own set of skills, like being an excellent duellist or having a deep understanding of certain types of magic that enable her to come to Harry's aid.
Theodore Nott could be another main character. He might be a friend of Daphne or her future husband. In the fanfiction, he could be involved in the events leading up to the marriage, like helping with the preparations or being part of a sub - plot where he has his own feelings or motives regarding the marriage. Additionally, Luna Lovegood could make an appearance, adding her unique perspective to the story and perhaps being a friend to Daphne during this important time.
Obviously, Harry Potter is one of the main characters. He is the one being adopted into the Greengrass family. Then, the Greengrass family members are important. There are likely to be the parents of the Greengrass family, and the Greengrass sisters. We might see Astoria Greengrass and her sister (if she has one in the fanfic). These characters will play significant roles in Harry's new life and the development of the story.
One possible plot could be that Harry, for some reason, has to leave the Dursleys earlier than in the original story. The Greengrass family takes him in. Maybe Daphne Greengrass and Harry become friends and study magic together. They could also face some threats from the Dark side, and Harry's presence in the Greengrass family might put them in danger, but they all stand together to fight against it.
Well, one interesting plot could be Harry learning the unique traditions of the Greengrass family. Maybe he discovers some ancient magic secrets that the Greengrasses have been guarding for generations.
Harry Potter is the main character for sure. In addition, Dumbledore or other Hogwarts professors could make appearances. They might come to check on Harry or give him advice regarding his new life in Potter Manor. There could also be some family members from the Potter family tree, who were thought to be long - gone but now reappear in the form of memories or spirits in the manor.