Well, if they had lived in Harry Potter fanfic, the story could have taken a much more complex turn. Maybe they would have joined Harry in his fight against Voldemort. Their unique skills or knowledge could have given the Order of the Phoenix an edge. For example, if they were really good at potions, they could have brewed some powerful antidotes to the dark magic-induced poisons that Voldemort's followers used. It might also change the relationships among the characters. Harry might have found new friends or allies, which could have affected his decisions and actions throughout the series.
They would probably interact the most with Harry, Ron and Hermione. Since these three are at the center of most of the action in the Harry Potter world, it's natural that if they were in the fanfic, they would be drawn to them. Harry is the hero, and they might want to help him in his quest. Ron is always up for an adventure and Hermione has the knowledge, so they could all form a great team together.
I'm not entirely sure as I haven't read this specific fanfic. But it might involve Harry Potter having more interactions with his godfather, Sirius Black, who in this fanfic presumably has some new adventures or a different role to play in Harry's life.
The main characters would probably start with Harry Potter. He is the central figure in most Harry Potter - related stories. Then, of course, the godfather who lived, which is most likely Sirius Black. Additionally, Dumbledore could also be an important character. He is a very influential figure in Harry's life and in the wizarding world in general. His wisdom and guidance might play a role in how Harry and his godfather interact and deal with the various challenges that come their way in this fanfic.
Maybe it's a twist to explore Neville's potential and show a different outcome. It could be that the author wanted to give him a chance to shine and be the hero instead of Harry.
It could be that the character's development doesn't match the original or expected traits. Maybe they act out of character or the story takes an unexpected turn with this aspect.
The story might explore alternate timelines or what would have happened if Harry Potter's special status didn't exist. It could lead to unexpected character developments and new conflicts.
In this fanfic, the Dursleys may be depicted as being in over their heads. Vernon Dursley, for example, might be shown as constantly angry and trying to assert his authority in a situation where he has none. Petunia Dursley could be portrayed as being torn between her dislike for magic and her sense of family obligation towards Harry. Dudley might be shown as being bullied or affected in the Muggle world because of Harry's presence in their family.
It varies a lot. Sometimes it's about changing the destiny of the character. Other times, it focuses on exploring alternate storylines and character relationships.
Well, a big difference could be in the way the story unfolds. Maybe the fanfic gives a twist to Harry's character or changes key events. Similarities might include the use of magic and familiar settings. However, the tone and focus could vary a lot.