There's a fanfiction named 'The Protective Sirius'. Here, Sirius's desire for Harry is centered around protecting him from the threats in the wizarding world. It shows their bond from a more platonic, protective angle.
Well, one interesting aspect could be the exploration of an unusual relationship dynamic. It takes two characters from the Harry Potter universe and imagines a connection that isn't in the original books. This can lead to new character development for both Sirius and Harry.
I'm not sure about specific 'sirius black desires harry' slash fanfiction. You can try searching on some well - known fanfiction websites like Archive of Our Own. There are a large number of Harry Potter - related fanfictions on it, and you might be able to find what you're looking for by using relevant keywords in the search bar.
Well, 'The Sirius - Harry Connection' is also a notable one. In this fanfiction, it's not just about Sirius desiring to be a part of Harry's life in a normal sense. It goes deeper into how Sirius might have influenced Harry's growth and his understanding of the wizarding world on a more profound level.
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.
It could develop in a complex way. The spanking incident might initially create tension between them. Harry could be angry or resentful towards Sirius at first.
Another aspect of this fanfiction could be that Harry uses his Parseltongue ability to communicate with the snakes in Azkaban (if there are any). The snakes might have some information about Sirius since they can sense the emotions and secrets of the prisoners. Through this unique method, Harry gets closer to proving Sirius's innocence.
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.
Well, a popular one is 'Sirius and Harry: A Different Kind of Family'. In this fanfiction, Sirius actually gets a chance to be a proper father figure to Harry. It shows their relationship evolving in a very heartwarming way. There's also 'The Sirius - Harry Connection'. This one plays around with the idea of a magical bond between them that goes deeper than what was shown in the books. And 'Harry's Refuge with Sirius' where Sirius provides a safe haven for Harry during tough times at Hogwarts.
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.