Ella doesn't realize she's interested in Char until more than halfway through the narrative—but we sure do. Up to that point, he is kind, friendly, and interested in her welfare, but it's not until they begin their correspondence that she begins to develop feelings for him (he, on the other hand, has apparently been crushing on her for a while). Of all the people in Ella's life, he seems the least interested in telling her what to do, which is one of the reasons he's such a good match for her.
Plus, neither of them particularly cares for propriety, which means they can bond over things like sliding down stair rails together. Wonder if they'll still do that when they're king and queen?