If Harry were to break a promise he made to Sirius. Promises are important, and if Harry fails to keep his word, Sirius might get angry. For instance, if Harry promised to stay out of a certain place or not to use a particular magic, and then did it anyway.
It could be that in the fanfiction, Harry is competing with Sirius in some way, like for the attention of a certain character or for a position in an organization. Harry's actions during this competition might make Sirius mad, especially if Harry uses underhanded tactics or if he doesn't respect Sirius's experience and seniority.
Perhaps in the fanfiction, Sirius is mad at Harry because Harry has befriended someone Sirius doesn't trust. Sirius, being protective of Harry, might see this new friendship as a threat. He could be worried that this person will lead Harry astray or put him in danger, and his anger towards Harry stems from his concern for Harry's well - being.
One possible reason could be that he's worried about Ginny's safety during the pregnancy. He might be overprotective and his concern comes out as anger.
It could be that Ron's actions were causing problems within the Order of the Phoenix. If Ron was being stubborn and not following the plans or orders set by the Order, which Sirius is a part of, Sirius might get angry. He would be frustrated with Ron for not being a team player and potentially endangering the mission and the lives of others.
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.
Well, perhaps Sirius proves his loyalty by protecting Harry from danger. For example, he might fight off some dark creatures that are after Harry. This shows Harry that Sirius is someone he can rely on.
One possible event could be a false accusation within the wizarding community. Maybe someone frames Harry for a serious crime, and his so - called friends believe it without really giving him a chance to defend himself. Another event could be a power struggle within Hogwarts or the wizarding world in general, where people see Harry as a threat and turn against him to gain an advantage.
In fanfiction where Harry is Sirius Black's son, the consequences are numerous. Firstly, Harry's inheritance would be different. He might have access to more of the Black family's wealth and heirlooms. Secondly, his relationship with other characters would shift. For instance, Hermione and Ron might see him in a new light. The whole dynamic of the Order of the Phoenix could also be altered. Sirius would be more protective and involved in Harry's life, which could lead to different strategies in the fight against Voldemort. It could also change how Harry views himself and his place in the wizarding world, as he would now be part of a different family legacy.
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 reason could be the strong bond between them in the original story. Fans might have felt that it could be developed into a father - son relationship in fanfic.
A gay Sirius Black fanfic might focus on his life outside of Hogwarts as well. He could be part of a wizarding community that is more open - minded about homosexuality. The story could show his journey of finding love and acceptance among his peers, while also dealing with the prejudices that still exist in some parts of the wizarding world.