One popular type of fanfiction about James Sirius Potter might be his adventures at Hogwarts. Writers could explore his relationships with his friends and family, like how he deals with the legacy of his famous father, Harry Potter. Maybe he gets into some mischief in the same way his father did, but also has to face new challenges specific to his own time at the school.
It could be a crossover fanfiction where characters from Doctor Who interact with those from Harry Potter, especially Sirius and James. Maybe they travel through time and space together or face some magical adventure.
Yes, there are quite a few. You can start by looking on fanfiction platforms like Archive of Our Own. Some fanfics might focus on their adventures during their school days at Hogwarts, exploring their deep friendship and the bond they share as if they were twins in a sense. They might get into all sorts of mischief together, just like in the original Harry Potter stories.
One possible scenario could be that McGonagall meets James Sirius Potter in a Hogwarts corridor. She might be reminded of his father, James Potter. She could give him some sage advice about living up to the Potter name and the importance of using his talents for good, just as his father did in his own way.
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.
It might happen if James doesn't follow Harry's instructions or does something dangerous. Like when he experiments with forbidden magic or disregards Harry's warnings about certain magical creatures.
Their relationship was like brothers. They supported each other through thick and thin. James welcomed Sirius into his group of friends wholeheartedly, and Sirius was always loyal to James. They shared secrets, like the creation of the Marauder's Map, and had a lot of fun together.
Sirius Black and James Potter were best friends at Hogwarts. They were both in Gryffindor. James was the leader of their group which also included Remus Lupin and Peter Pettigrew. Sirius was from the Black family, a pure - blood family with dark wizarding traditions, but he rejected their beliefs. He and James were known for their mischief, like creating the Marauder's Map. They also supported Remus during his werewolf transformations. Their friendship was strong until James was killed by Voldemort.
The fanfiction 'When James Fell Ill' is also quite good. It delves into how James Sirius Potter copes with being sick in a wizarding world full of potions and spells. It shows his vulnerability and the support system he has in place.