It is often not included in lists of the Spanish nobility because it is rare: princely titles are now reserved for members of the royal family (the heir to the throne or the consort of the Queen regnant).
It is often not included in lists of the Spanish nobility because it is rare. Prince/Princess are English translations of Infante/Infanta, referring to the son or daughter of a king; such titles are reserved for members of the royal family (the heir to the throne or the consort of the Queen regnant).