The 'Harry Potter' books are set in a magical world full of its own stories, prophecies, and secrets. Sirius is a complex character with a lot on his plate. He has to deal with his family history, his time in Azkaban, and his loyalty to his friends. Fanfiction is a form of creative writing by fans outside the original story. Sirius doesn't have the time or the inclination within the context of the story to be reading fanfiction. His life is too filled with real magical drama and danger.
Well, if Sirius read fanfiction, it could open up a whole new side to his character. Maybe he'd start to question some of the things he thought were absolute in the wizarding world based on the creative ideas in fanfiction. But realistically, he has so much going on in his life - from trying to clear his name to protecting Harry - that it's hard to imagine him actually taking the time to read fanfiction. He's more of a doer in the real magical world than a consumer of fan - created fictional works.
One possible aspect could be how Harry's Animagus form might change the dynamics between him and Snape in slash fanfiction. For example, if his Animagus form is something small and unassuming like a mouse, it could lead to some interesting stealthy interactions with Snape. He might be able to observe Snape in ways he couldn't as a human, adding a new layer of intrigue to their relationship in the fan - created story.
Yes, it could potentially be a popular genre within the fanfiction community. Fanfiction allows for a great deal of creative license, and fans often like to explore different aspects of character relationships. The concept of Harry Potter submitting to Sirius Black might attract those who are intrigued by the mentor - mentee relationship between them taken to an extreme level. It could also be popular among fans who enjoy stories with elements of loyalty, trust, and power play. However, it's also likely to be controversial as it can be seen as changing the fundamental nature of the characters too much for some readers.
One great 'Harry Potter Sirius and Remus fanfiction' is 'All the Young Dudes'. It beautifully delves into their relationship and backstories. It shows their time at Hogwarts, their friendship, and how they dealt with the challenges around them. The characterizations are spot - on, making it a very immersive read.
There could be. The idea of Harry being the kid of Remus and Sirius is an interesting and somewhat alternative take on the original story. Some fanfiction writers like to explore different family relationships and backstories for the characters. You could try searching for it by typing in the exact phrase 'Harry Potter is Remus and Sirius kid' in the search bar of popular fanfic platforms.