And I suppose that’s why I’ve always liked the idea of Ron and Hermione together: because it didn’t feel inevitable, and because however right they eventually seemed together, I could see the potential for conflicts, the work that was to come. Ron and Hermione don’t even like each other when they meet. They squabble about rule-breaking, and later about Hermione’s cat’s apparent predations on Ron’s pet rat Scabbers (who, to be fair, turns out to be a fugitive dark wizard in disguise). At various points in the series, Ron and Hermione are patently jealous of each other’s light romances, and handle that jealousy badly.
So one of the reasons Ron and Hermione’s attraction to each other feels durable and real is that we can see how it grows over the course of the series, and how the characters overcome an initial antipathy. Hermione, who enters the stage as a rule-obsessed busy-body, and who becomes rigid in her definitions of justice and fairness in the matters of Crookshanks and Scabbers, comes to learn that there are higher ideals than the regulations governing the conduct of the Hogwarts’ student body, and more important achievements than being the first to answer any given professor’s question. She also develops an actual sense of fun over the course of the series thanks to her affiliations with Harry and Ron, which makes Hermione a vastly more appealing person than the anxious, newly-minted witch we meet at the beginning of the story.
Ron, by contrast, comes to understand that self-gratification and rebellion for rebellion’s sake are not particularly meaningful ends towards which to orient one’s life. Some of these changes are due to the internal dynamics of his own family: Percy’s self-righteousness fractures the Weasleys’ strong sense of loyalty to each other, while Fred and George come to employ their talents for mischief in the causes of Hogwarts’ integrity and the fight against Voldemort. But they’re also due to Hermione’s influence. Ron comes to admire her academic gifts and her intellectual curiosity, and ultimately to share her concerns, working on issues like the appeal to save the life of a hippogriff. It’s no mistake–and entirely in keeping with the series’ idea that political convictions and political work forge remarkably powerful connections between the people who share them–that Ron and Hermione first kiss when Ron, who initially dismissed Hermione’s concerns for the welfare and labor rights of Hogwarts’ house elves, frets about their fate during the Battle of Hogwarts. For both characters, their investment in each other leads them to overcome some of their clearest weaknesses and flaws of character.