It could be that Harry's glasses disappear as a result of a magical experiment gone wrong. For example, Hermione might be trying out a new spell she read about in an ancient book, and it backfires, causing Harry's glasses to vanish. This would create a bit of a rift between them at first, but they would soon realize that they need to work together to reverse the spell and retrieve the glasses.
It could slow down the plot. For instance, if Harry's glasses are constantly malfunctioning, he might miss important clues or signals. This would add more obstacles to his journey of solving mysteries or fighting against the dark forces.
In this fanfiction, his glasses could have a disorder where they constantly fog up, no matter the temperature or humidity. It would be really annoying for Harry. He might be in the middle of a battle with Death Eaters or trying to solve a mystery in Hogwarts, and he has to keep wiping his glasses to see clearly.
A jinx from a rival student could make Harry's glasses disappear. Some Slytherin student who doesn't like Harry might play a cruel prank by using a vanishing jinx on his glasses.
Perhaps there's a plot against Harry by some dark forces, and the Potters believe that only they can protect him properly. They might think that the people who have been taking care of Harry so far are not equipped to handle the new and more dangerous threats. Also, it could be that the afterlife in the wizarding world has some rules or opportunities that allow them to try and get Harry back into their family fold. They could have been given a second chance, so to speak, and are eager to take it.
Yes, they might. Just like any other group of people, those who identify as Blacks or are part of the Potter family name (if we assume there are real people with that name) could be fans of the Harry Potter series and thus read fanfiction. Fanfiction offers a wide range of interpretations and extensions of the original story, and anyone with an interest in the magical world of Harry Potter could be drawn to it.
One possible motive could be that the Potters discovered some dark plot by the Malfoys involving Harry. Maybe they found out that the Malfoys were planning to indoctrinate Harry into their pure - blood supremacist ideology against his will. So, to protect Harry from that, they kidnapped him.
Sirius Black could also be part of it. He was Harry's godfather. He might have escaped from Azkaban earlier in this fanfic. He teams up with the Potters to rescue Harry. He could be the one who scouts out the Dursleys' house before the actual rescue operation, using his skills as an Animagus to stay hidden.
It could also be that the Potters are under some sort of magical influence or curse. In the fan fiction world, there could be a dark force at play that makes them see the twins as more important. This force might be manipulating their emotions and perception, leading to the neglect of Harry.
One possible reason could be that the twins might have some special abilities or circumstances that draw the Potters' attention more. Maybe they are more outgoing and seem to need more immediate care or guidance. Another reason could be that there is some sort of miscommunication or misunderstanding within the family. For example, the Potters might think Harry is more self - sufficient when in fact he also needs their love and attention.