One popular 'kingdom hearts baby fanfiction' is 'The Adventures of Baby Sora'. It's really cute as it imagines Sora as a baby in the Kingdom Hearts world, getting into all sorts of innocent mischief. Another one could be 'Baby Roxas' story where we see Roxas in his baby form experiencing the world in a very different way.
Well, there's this 'kingdom hearts baby fanfiction' where they explore what would happen if the keyblade masters were babies. It's a really interesting take as it shows how different their personalities might be at such a young age. And also, some fanfictions in this genre focus on the baby versions of the villains, like how a baby Xehanort might start his journey towards darkness in a more innocent - yet still menacing - way.
In the realm of 'kingdom hearts baby fanfiction', a lot of them play with the idea of baby versions of the characters interacting with the normal - sized characters. For example, a story might have baby Kairi befriending the adult Donald and Goofy. It's really endearing to see how the writers handle these interactions, with the baby characters often having a sort of innocent charm that makes the story unique. These fanfictions can also add new elements to the Kingdom Hearts lore, like how the baby characters might have a different connection to the heartless or the different worlds.