Disney's Beauty and the Beast

If the rose won't wilt 'til his 21st birthday, how old was the prince when he was cursed?

Also, where were his parents? And why did the prince open the door himself?

I kinda want to write dark AUs for all of the Disney movies, and here's how I could see it going for this one:

Maurice is put into the sanitarium immediately after getting back after Belle took his place. He dies there.

When Belle looks into the mirror, she sees him in a pauper’s grave.

Things devolve into Twisted Princess Belle from there.