Hogwarts was started by the 4 greatests witches and wizards of their time but none of the 4 were considered royal. The only kings and queens mention in the books were chess pieces. Are the kings and queens that belong to Wizard Chess true royals that werer placed under a spell by a former wizard? Will one of their decendants appear and try to restore the chess pieces to their former kingdoms?
On another website, the HBP was described as an old man with gray hair like a lion and yellowish eyes behind the spectables. It is possible that the HBP could have been transfigured into an animal waiting for the spell to be broken by someone like Harry Potter.