One possible reason could be a misunderstanding. Maybe some false information was spread about Harry that made Sirius believe he had done something unforgivable. For example, if there were rumors that Harry was involved with dark magic in some way, Sirius, who has a strong aversion to the dark side, might be quick to disown him.
Perhaps in the fanfiction, Sirius discovers something about Harry's lineage that he cannot accept. Maybe there is a hidden connection to a dark wizard in Harry's family tree that Sirius feels goes against his principles. Or it could be that Sirius is trying to protect Harry in a strange way. He might think that by disowning him, he is keeping Harry away from the dangerous life that Sirius himself is leading, thinking that his association with Harry will only bring harm to the boy.
It could also be due to some external influence or manipulation. In the wizarding world, there are powerful forces at play. If someone was able to cast a spell on Sirius to make him think ill of Harry, or if they used some form of mind - control, it could lead to him disowning Harry. Another aspect could be related to Sirius's own past traumas. His family history and his experiences in Azkaban might have made him more volatile in his relationships, and a small trigger related to Harry could cause him to make such a drastic decision.
A common reason could be misinformation. In the wizarding world, rumors can spread quickly. If a false rumor about Harry being involved in dark magic activities got to Sirius, he might disown him. For example, if someone planted evidence that Harry was secretly communicating with Death Eaters.
In some fanfictions, it could be due to dark magic influence. A spell or a dark force might have corrupted Sirius's mind, making him turn against Harry.
One possible reason could be miscommunication. Maybe Harry does something that Sirius misinterprets as a betrayal or a stupid mistake, leading to Sirius lashing out.
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.
Fanfiction about these three can take many forms. For example, there could be time - travel fics where Harry goes back in time and meets Regulus and Sirius when they were younger. This could lead to all sorts of interesting plot twists, like Harry trying to prevent Regulus from joining the Death Eaters in the first place. Or it could be a fic where Sirius survives and he and Harry explore the secrets of the Black family together, including things that Regulus left behind. There are also fics that focus on the emotional bonds between the characters, showing how the different personalities of Regulus, Sirius, and Harry interact and influence each other.
Well, if Sirius Black hates Harry Potter fanfiction, it could lead to a divide among fans. Some fans might respect his view and be more critical of fanfiction themselves, while others might disregard his feelings. Also, it could potentially limit the creativity within the fan community as people might be afraid to create content that could be seen as disrespectful to Sirius Black's character.
One possible plotline could be that Sirius Black has been under some dark magic influence. Maybe a powerful dark wizard has managed to manipulate his mind, making him believe Harry Potter is a threat to him or the wizarding world in some false way. This could lead to a series of events where Harry tries to prove his innocence and figure out what's wrong with Sirius. Another could be that there's a misunderstanding based on some prophecy or false information spread within the wizarding community. Sirius, being impulsive, jumps to conclusions and decides to disown Harry without fully understanding the situation.
One reason could be the strong bond between them in the original story. Fanfic writers might think that making them father - son would enhance that bond further. Also, Sirius was a very important figure in Harry's life, so it makes for an interesting twist.
One great 'Harry Potter Sirius Black fanfiction' is 'Padfoot Returns'. It really delves into Sirius's character and his relationships within the wizarding world. The story has a great plot that keeps you hooked from start to finish.
There probably is. The Harry Potter fandom is huge and full of diverse ideas. Writers might explore this idea to add new twists to the story, like how Harry's relationship with Sirius would be re - imagined if he were his daughter, and how it would change the overall plot dynamics.