I always feel sorry for Petunia. She was the older sister, and I'm sure that even though her parents didn't mean to do so, they probably made a bigger fuss of Lily. I can imagine how Petunia's A grades would be overshadowed by Lily's B plus in Charms (What IS Charms?!)

What I'd like to know - however - is why JK gave Petunia such a name, and ... well, Lily is lovely - Petunia just cries for ridicule. I always get mad when people make Petunia act ten times more idiotic and mean than she normally is -

She's an interesting character, and should be developed, if not in the real books, at least someone ought to give her the benefit of doubt in fanfics.