"daughter of the 'Catholic Kings' of Spain, Ferdinand and Isabella"
The kingdoms of Castile and Aragon
Creative Commons Attribution Share AlikeThe kingdoms of Castile and Aragon - Credit: Corona de Castilla
 Ferdinand and Isabella, the Catholic Monarchs, reconciled the two warring kingdoms of Castile and Aragon and formed a united Spain with their marriage in 1469.  Both were monarchs in their own right, Isabella I of Castile and Ferdinand II of Aragon. 

 

The title 'Catholic King and Queen' was bestowed upon Ferdinand and Isabella by Pope Alexander VI in 1496, and they reigned together until Isabella's death in 1504.  Credited with the establishment of modern Spain, they are also renowned for their use of the Inquisition.

 

Catherine of Aragon. Artist unkown. 16th century
Public DomainCatherine of Aragon. Artist unkown. 16th century - Credit: Wikimedia Commons

  Ferdinand and Isabella's fifth and last child, Catherine, married Prince Arthur, eldest son of Henry VII and heir to the English throne.  After Arthur's premature death, she married his brother Henry VIII and became Queen Catherine of England, Catherine of Aragon.