Vosotros?

I saw Pan's Labyrinth last night, and it was every bit as enchanting and shocking and incredible as everyone had led me to believe it would be...I was absolutely thrilled with it.

It was also fun for me to listen to the gorgeous Castillian Spanish as I read the subtitles, and to see the subtle mistranslations (as i saw them) and also some bits that were untranslatable.

To wit: I never did learn the vosotros verb tense.

You see, there is a familiar 'you' tense and a formal 'you' tense. And there is, ostensibly, a familiar 'you' plural and a familiar 'you' singular. But in modern Spanish, for the most part, folks don't use the familiar plural 'you.'

But the faun addresses young Ofelia. the princess, as 'vos.' I noticed it. And I wondered.

You experienced Spanish speakers: help? Is 'vosotros' a normal way of addressing royalty? Or, child royalty? And if so, why? Certainly, 'nosotros,' or 'we,' would be expected for royalty addressing the people. So the you-plural makes sense, but if so, why the familiar and not the formal 'ustedes'?

Anyone? deadwinter?