A vampire monarch is a vampire who rules over a kingdom of vampires. Every monarch has authority over his or her vampire subjects, however they still remain under the Vampire Authority in the hierarchy, this hasn't always been the case though as stated by Nan that vampire monarchy goes back further than the Vampire Authority and had in the past more power. Upon the death of a reigning monarch, the Vampire Authority will appoint a new king or queen.
When two vampire monarchs marry, an allegiance is formed between them. Upon the death of either one, the other becomes the ruler of both. When Russell Edgington was entombed, as their marriage eventually becomes recognized by the Vampire Authority. Queen Sophie Anne of Louisiana, as his widow also becomes the Vampire Queen of Mississippi before her death, after which Bill Compton becomes the King of Louisiana.
A vampire Kingdom can be split into districts which are governed by an appointed Vampire Sheriff who serve under the reigning King or Queen of the State. Those who closely serve a king or queen are considered to be members of their royal court.
It is not yet know if age or status has anything to do with crowning a king or queen, but it is assumed that a vampire has to have done something very significant or impressive enough to be granted the title of king or queen (as a relatively young vampire Bill Compton managed to reach the rank of vampire king simply by helping the AVL destroy Sophie-Anne Leclerq
, the previous monarch, for selling vampire blood)