It's possible that in the cave, they start to see each other as equals rather than just a mentor - student relationship. They might argue about the best way to deal with the cave's mysteries at first, but through that process, they learn to value each other's perspectives. Also, if one of them gets injured in the cave, the care and concern shown by the other would enhance their relationship.
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.
Well, at first, Sirius would be in a state of shock and panic. But then he'd have to step up. Their relationship would shift from one of equals (in a sense, as Harry was growing up) to a caretaker - cared - for dynamic. Sirius would have to learn about Harry's likes and dislikes as a baby. He'd sing lullabies to him, comfort him when he cries. This new experience would make their bond stronger in a very different way. Harry might not remember all of it when he's turned back, but there would be a subconscious change in how he feels towards Sirius, a deeper sense of security and love that stems from those baby - days when Sirius was his whole world.
It may explore the emotional bond between them. Sirius could be like a father figure to Harry. He gives Harry advice and guidance, which is different from what Harry gets from others. This special connection makes Harry trust Sirius more than anyone else.
The relationship could become strained. Sirius might start to view Harry differently, with a bit of wariness. He might not trust Harry as much as before in terms of making good decisions. But it could also lead to a more open relationship where they talk about things they previously avoided, like relationships and feelings.
Well, it could be that in the cave, Harry discovers some long - lost secrets about his family. Sirius, being there, helps him make sense of these revelations. They might have to solve some complex magical puzzles to progress further in the cave.
At first, it might be a bit rocky. Harry is used to a more structured upbringing at the Dursleys', while Sirius is quite the free spirit. But as time passes, Sirius starts teaching Harry about his family heritage. They go on adventures together, like exploring the Forbidden Forest. Harry begins to see Sirius as a true father figure, and Sirius sees Harry as the son he never had. They also have arguments, like when Sirius is overprotective, but they always work through it, which deepens their relationship.
At first, their relationship would be filled with confusion. Harry might be shocked and Sirius would be equally bewildered. But as they start to accept the situation, they could develop a deeper understanding of each other. Sirius could become more of a parental figure to Harry in a different way, and Harry could offer Sirius a new sense of purpose.
In this type of fanfiction, the relationship is often explored through emotional depth. For example, Sirius might be portrayed as a mentor to Harry, guiding him through the difficult world of magic. It could also show their shared experiences of loss, which bonds them closer. Maybe Sirius shares his memories of James with Harry, strengthening their connection.
Well, their relationship would be in tatters. Harry would probably avoid Sirius like the plague after such an event. Sirius, on the other hand, would be at a loss for how to deal with what has happened. He might feel betrayed, even though he knows Harry was forced. This would create a huge rift between them that would take a lot of time and effort, if ever, to mend. It would also change the way they interact with other characters in the fanfiction, as their relationship was an important part of the overall story dynamic.
Sirius' character development could involve him coming to terms with his own past traumas while rescuing Harry. He may have to face his fear of Azkaban and the dark magic that he has encountered in his life. As he rescues Harry time and time again, he becomes more confident in his own abilities and his place in the fight against Voldemort. He also starts to see Harry as more than just James' son, but as an important part of the wizarding world's future, which makes him more committed to protecting Harry at all costs.