I think Goblet of Fire would have really been the point for them to hit it off and toy with the idea of being together, but that asian persuasion got Harry distracted. And Hermione with Krum. Ron got jealous about that, if I recall?

I've been there. I'm actually not gonna be able to hang on very long tonight. My head's starting to pound X.X

Better safe than sorry and needing to edit. <3