Hermione would surely be involved. She could be Harry's research partner, helping him find relevant medical information in books and scrolls. Her intelligence and thirst for knowledge would be very useful in exploring new areas of medical magic. Another character could be Madam Pomfrey. She could be Harry's mentor, teaching him the basics of wizarding medicine and guiding him in his new role as a medic.
The dragon, of course, is a major character. It could be named something unique like 'Fyrstorm'. There might also be Hermione and Ron. Hermione would probably be worried about the legality and danger of raising a dragon, while Ron might be both scared and a bit excited about it.
One possible main character could be a Martian elder who takes Harry Potter under their wing and helps raise him. This Martian elder could have special knowledge about the planet and its hidden magic that they pass on to Harry.
The supreme Mugwump himself could be a main character. He might have his own backstory, motives, and goals that drive the story forward.
Hermione could be a main character. She would probably be very involved in helping Harry with the baby, using her vast knowledge of magic to ensure the baby's well - being.
Hermione could be a main character. She might help Harry understand the implications of being heir to multiple houses. Ron could also be important as he stands by Harry through all the new revelations. There could also be characters like Draco Malfoy. If Harry is heir to Slytherin, Draco's attitude towards Harry might change significantly, adding an interesting dynamic to their relationship.
Well, first off, Ursula is an obvious main character as she is related to Harry in this fanfiction. Then there's Hagrid. He has always been there for Harry and would likely play a role in helping Harry deal with this new situation. Neville could also be an important character. He might be one of the few who initially believes in Harry and doesn't immediately turn his back on him because of his new identity. And then there are the Weasley family members. They might be a bit hesitant at first but would eventually come around to help Harry as they have always been a big part of his life at Hogwarts.
I think Dobby could be an important character. Since Harry is raising himself, Dobby might take it upon himself to secretly help Harry. He could provide some food and small comforts when Harry is all alone. Another character could be Hedwig. She would be more than just a pet; she could be Harry's only true companion, helping him in small ways like delivering messages or even warning him of danger.
Hermione is often a key character. She might stand by Harry's side, using her intelligence and loyalty to help him through the tough times. She could be the one to encourage him to keep going and not let the disownment break him.
Hermione is often in these fanfictions. She might help Harry understand the more complex magical aspects related to his broomstick. For example, she could research ancient spells that were once used to enhance broomstick speed and try to apply them to Harry's broom.
Hermione is often a common character. Since she is Harry's closest friend, she usually plays an important role in helping Harry navigate the past. She might use her vast knowledge of magic and history to figure out why Harry was summoned and what they need to do next.