In fanfiction, the development of Batman and Superman's brotherly relationship can be a complex and fascinating journey. At first, they may clash due to their distinct personalities and approaches to justice. However, as they come to terms with their brotherhood, they begin to understand and support each other on a deeper level. For example, Superman might help Batman see that there is more to the world than just the dark alleys of Gotham, while Batman could teach Superman about the importance of strategy and preparation. This new - found bond can lead to them teaming up in ways that are different from their usual partnerships, facing threats that neither could handle alone. Fanfiction allows for a rich exploration of this relationship, with writers delving into their emotions, shared values, and the growth that comes from their unique connection.
Well, often in fanfiction, their brotherly bond is formed through some kind of shared experience. Maybe they discover they have the same origin or are part of some greater cosmic plan. Their relationship might develop with them protecting each other more. Superman could use his super strength to shield Batman from danger, and Batman could use his detective skills to solve problems that Superman might overlook. It's an interesting dynamic that can be explored in countless ways in fanfiction.