One possible storyline could be that Sirius helps Harry deal with the trauma of his parents' death in a more direct way. Since Sirius knew James and Lily well, he could share personal stories about them, making Harry feel more connected to his parents. Another could be Sirius training Harry in advanced magic earlier than he would have learned at Hogwarts, giving him an edge against Voldemort. And finally, Sirius might introduce Harry to a whole new side of the wizarding world that he hadn't seen before, like the more rebellious and free - spirited parts of the magical community.
A plotline might involve Sirius and Harry living together and Sirius trying to give Harry a normal family life. He could cook for Harry, help him with his homework, and they could have a pet together. Maybe they get a Kneazle, and Harry learns to take care of it with Sirius' guidance. This would be a contrast to the cold and often neglectful treatment he received from the Dursleys. And as Harry grows, Sirius could introduce him to his old friends like Remus Lupin in a more family - like setting, strengthening Harry's support system.
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 the son has to deal with the stigma attached to his father's name. Some students might be afraid of him or look down on him because of Sirius Black being a supposed mass murderer. But as he grows and shows his true character, he could change the perception of those around him. He could also discover some hidden magic or powers that were passed down from his father, which could help him in his adventures at Hogwarts and beyond.
One interesting storyline could be Sirius Black surviving the Battle of the Department of Mysteries and then helping Harry train secretly for the final battle against Voldemort. He could teach Harry some advanced magic that he learned from his time in Azkaban and the Order of the Phoenix.
In a fanfiction where Sirius Black adopts Hermione Granger, a plot twist could be that the magical community doesn't accept this adoption easily. There could be a lot of opposition from different factions. Some might think that Sirius, with his past as a supposed criminal, isn't a suitable guardian. Meanwhile, Hermione could be facing problems at Hogwarts because of this new family situation. However, through their bond, Sirius and Hermione could overcome these difficulties and in the process, Hermione could learn some long - lost family magic from Sirius, which gives her an edge in dealing with the challenges that come their way.
One possible plotline could be Harry learning more about his parents from Sirius. Sirius could share all the little details, like how James was in school, his mischievous deeds, and how he courted Lily. This would give Harry a deeper connection to his family's past. Another could be Harry and Sirius training together in magic, especially in defensive spells. Sirius, being a skilled wizard, could teach Harry some unique spells and techniques that he might not learn at Hogwarts. Also, they could have adventures in the wizarding world together, exploring places that are off - limits to most students.
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 interesting storyline could be Sirius Black protecting baby Harry from the remaining Death Eaters. He uses his skills as an Animagus to outwit them and keep Harry safe. For example, he might transform into his dog form to lead them astray while secretly hiding Harry in a magically protected place.
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.
One potential storyline could be Sakura struggling to live up to Tsunade's expectations. Tsunade is a legend, and Sakura might feel pressured. Another could be Sakura getting involved in Tsunade's past - related mysteries. Maybe there are some secrets about Tsunade's early days that Sakura helps uncover. And of course, there could be a storyline about Sakura using the knowledge she gets from Tsunade to protect the village in a big way.