There could be old friends from their school days. For instance, a classmate who knew some deep secrets about them. Maybe this friend was also in the same secret club or society that his parents were part of, and after their deaths, this friend tried to keep an eye on Harry from the shadows.
There could be powerful wizards or witches who were allies of his parents. These characters might have been in a magical pact with Harry's parents to protect certain magical artifacts or knowledge. After his parents' death, they are waiting for the right time to reveal the truth to Harry and enlist his help in a greater magical mission.
Well, it could be two powerful Aurors who were thought to be dead but were actually in hiding. They might have been fighting against Voldemort's forces and had to disappear to protect their family. Maybe they were friends with James and Lily Potter and got caught up in the same battle that led to the Potters' death.
One possibility could be that Harry is the son of a powerful but mysterious wizard and a muggle - born witch who had to give him up for some reason. Maybe his real father was a dark wizard who was hunted down, and his mother was a brave witch who wanted to protect Harry from that dark legacy.
In addition to the Potters themselves, there are often original characters created for the fanfiction. For example, there could be a wizard or witch who was friends with James and Lily at Hogwarts but was not mentioned in the original books. These characters can bring new plotlines and perspectives. Voldemort is also a crucial character in many of these fanfictions, as his actions are directly related to the fate of the Potter parents.
Well, a common concept is that Harry's real parents were actually involved in a prophecy that was much more complex than the one we know. Maybe they were trying to prevent a greater evil than Voldemort, and in the process, they had to make sacrifices that led to their seeming deaths. For example, they could have faked their deaths to go into hiding and protect Harry in a more covert way.
One possible reason could be that he might feel abandoned. Growing up without them, he could resent the fact that they left him an orphan. He might think that if they were really so great, they would have found a way to survive and be there for him.
His friends, like Ron and Hermione, are very likely to support him. They've always been there for him in the original story, and in this fanfiction scenario, they would be even more important in his life. Hagrid could also be a great source of support. He has a big heart and has always cared about Harry.
Obviously, Harry Potter is a main character. He's the one who has been forgotten by his parents. His friends Hermione and Ron might also play important roles as they usually do in helping Harry through his difficulties.
James and Lily Potter are the key characters as the whole concept is centered around them being in stasis. However, other characters like Sirius Black could also be important. Sirius was close to James, and his reaction to James' return from stasis could be an interesting part of the story. And then there are the villains or antagonists. There could be those who don't want the Potters to return, perhaps some remaining Death Eaters or a new, mysterious force, which would also make them important characters in the fanfiction.
One possible reason could be a misunderstanding. Maybe he discovers some secrets about his parents that he misinterprets. For example, if he finds out they were involved in some dangerous or morally ambiguous activities in their youth that he doesn't fully understand at first.
One possible reason could be that he discovers some long - hidden family secrets that make him question his parents' actions or decisions. Maybe he finds out about some dark deeds in their past that he can't overlook.