When Harry and Severus go back in time, Severus' relationship with the Death Eaters will surely be affected. He might avoid getting involved with them completely, which would change how the other Death Eaters view him. Harry's relationship with his friends like Ron and Hermione would also be different. Since he is changing the past, the future where he meets them might not be the same. And Severus' relationship with Hogwarts faculty could be improved as he has a chance to start anew without the burden of his past mistakes.
The main characters are Harry and Hermione, of course. Harry, the Boy Who Lived, with his Gryffindor courage and his special connection to Voldemort. And Hermione, the brilliant and studious witch, always full of knowledge and quick thinking.
The main characters are clearly Severus and Harry. Severus is a complex character, often portrayed as brooding and mysterious, with a deep knowledge of magic. Harry, on the other hand, is the hero of the main Harry Potter series, known for his bravery and his connection to Voldemort.
Definitely Hermione. Since she's Harry's closest friend and very intelligent, she would be deeply involved in any changes Harry tries to make. Also, Snape. Harry's actions in the past could completely change his relationship with Snape. And of course, Voldemort. If Harry goes back far enough, he could potentially stop Voldemort's transformation into the evil wizard he became.
Obviously, Harry and Teddy are the main characters. Harry is a well - known wizard from the original series, and Teddy is his godson.
Obviously, Harry is the main character. He's the one going back in time. Then there are the Marauders - James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. Lily Evans, Harry's mother, also often plays a significant role as Harry might interact with her in the past. Dumbledore could be another important character, as he might be aware of Harry's time - traveling or be involved in some way in the events that occur in the past.
Filch could be a key character too. Harry going back in time might mean more opportunities to outwit Filch and his attempts to catch students misbehaving. This would add a lot of comical moments as Filch is always so serious about his job and Harry could use his time - traveling knowledge to drive Filch crazy with his pranks.
Sasuke's relationship with Sarada could also be affected. If Sarada experiences things in the past related to Sasuke's family or his past actions, it could make her understand her father better. Maybe she'll come back with a new understanding and they'll have a more open relationship.
One possible plotline could be that Harry and Severus go back in time to prevent certain tragedies from happening in the wizarding world. For example, they might try to stop Voldemort's rise to power much earlier. Another could be that they go back to change their own relationship. Maybe in the original timeline they were enemies, but now they have a chance to become allies or even friends.
The 'big three' are likely to be the main characters. However, without more context, it's hard to say exactly who they are. They could be three powerful heroes or villains from a particular fictional universe.
There might also be other characters from the past that they meet. These could include ancient Greek heroes or mythological creatures. Their interactions with these characters will shape the story as they navigate through the past.