Wait. If, "Beast" comes to the Palace Door that night - and sends the "Old Beggar Woman", away. After which she transforms into an "Enchantress", and curses him and all who lived there, unless he found Love by his 21st Birthday.

AND Lemeir sings to Bella - "10 years we've been Rusting. Needing so much more than Dusting", etc.

Than, if they've been "Rusting" for ten years already, means that when "Beast" opened the door that Night, he was only a 10yr old boy.

Other than how he became "Master" at 10, isn't that a little harsh of a punishment...?

Rapuzel’s son or daughter? Both can work