It could be the original characters from the source material who have now aged 19 years. Their personalities might have changed a bit due to life experiences, but they still carry the essence of who they were.
Maybe it could be a combination of both. The older characters guiding and interacting with the younger ones. The relationships between them, like a mentor - mentee relationship or a family dynamic, could be a central part of the story. This would add depth to the plot as there would be different perspectives from different generations.
The children of Harry, Ron, and Hermione would likely be main characters. For instance, Harry's son could inherit his father's courage and be at the center of a new mystery. He might have to deal with the high expectations placed on him because of his father's legacy.
The main characters could be Ladybug and Chat Noir, who are now experienced heroes. However, the fanfiction could also focus on a new group of heroes that they are training. These new heroes could come from different backgrounds and have unique personalities. There might also be some characters from the past that have turned into antagonists due to some past grudges or misunderstandings. And of course, the Kwamis would still be there, guiding the new and old heroes alike.
Hermione Granger would be a likely main character. She has always been a central figure. Maybe she's working on some revolutionary magical research or is involved in political reforms in the wizarding world. Her relationship with Ron and their family life could also be part of the story.
Obviously Danny Phantom himself would still be a main character. His friends like Sam and Tucker would likely also be important. They've probably grown and developed new skills over the 10 years.
A young orphaned boy who has grown up in the chaos of the past 28 months. He has a unique perspective on the new world and his innocence and adaptability could make him a central figure in the story.
Obviously, Naruto himself would still be a main character, as he is now an important figure in the village. His son Boruto could also be a main character, as he might be following in his father's footsteps. And Sasuke would likely still play a significant role, perhaps as a mentor to the new generation.
Obviously, the children of the original characters like James, Albus, and Lily Potter. They are likely to be at the center of many stories as they navigate Hogwarts life. Also, Scorpius Malfoy as he is the son of Draco Malfoy and his story could be intertwined with the Potters.
Obviously, Harry and Hermione are the main characters. They are likely to be older, more mature versions of themselves. Harry, with his Gryffindor courage still intact, and Hermione, with her vast knowledge of magic.
The main characters are often the children of the original Harry Potter characters. For example, Albus Severus Potter, James Potter, and Lily Potter. Also, Scorpius Malfoy is usually a central character as he is part of the new generation at Hogwarts.
Newly discovered magical families could rise to prominence. These families might have been in hiding or just not known before, but now they play a crucial role in the wizarding world of 1000 years later. Their members could be the main characters, bringing in fresh perspectives and magical abilities that were previously unheard of.