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The Kallergis (Greek: Καλλέργης) family is a Cretan family said to be descended from Byzantine Emperor Nikephoros II Phokas (Latinized: Nicephorus II Phocas, Greek: Νικηφόρος Β΄ Φωκᾶς, Nikēphoros II Phōkas), and were at one stage rulers of Crete.
The history of the twelve byzantine rulers 
Emperor Alexios II Komnenos (Greek: Αλέξιος Β’ Κομνηνός, Alexios II Komnēnos) sent twelve noble Byzantine families to Crete, in order to strengthen the ties between the island and the city of Constantinople. The families were credited important land and administrative privileges. Ioannis Phokas was one of those 12 Byzantine rulers.
The Phokas name changed to "Kallergis" during the Venetian dominion. As Richard Coudenhove-Kalergi describes in his book An idea conquers the world the Kallergis name is composed of the Greek word kalon (=beautiful) and ergon. (Greek: Καλλ(ι)έργης > Καλλέργης, known in many versions as Kalergis, Calergis, Kallergi, Callergi, Calergi).
Large areas of Crete were attributed to each of those families. That is the reason that villages named Kallergiana  (Greek: Καλλεργιανά) in Kissamos or Kallergo  (Greek: Καλλέργω ή Καλλέργο) in Rethymno exist today. On the White Mountains (Greek: Lefkà Ori, Λευκά Όρη) there is also a mountain hill called Kallergis (altitude 1.650 meters).
Heraldic ensembles containing the Kallergis family coat of arms (bendy argent and azure) can be found all over the island of Crete, in churches and other monuments. The name reappears many times in the turbulent history of Crete but also of modern Greece.
Their prominent position and privileges survived during the Venetian dominion of Crete as they were part of the "privilegiati" (Greek: Αρχοντορωμαίοι) and sometimes of "nobili Veneti". They served many times the Venetian regime but at the same time defended the welfare of the Cretan people, being head of revolutionary movements against the Venetians.
- Alice-Mary Talbot,Denis F. Sullivan: The History of Leo the Deacon: Byzantine Military Expansion in the Tenth Century. Dumbarton Oaks, 2005, Book II, p. 80
- David Holton (ed.), Literature and society in Renaissance Crete, Cambridge University Press 1991, p. 80
- Melchior Vogüé (marquis de), Charles Henri Auguste Schefer: Revue de l'Orient latin, Volume 11 p. 111
- Richard Nicolaus Coudenhove-Kalergi (Graf von)An idea conquers the world, Roy Publishers 1954, p. 4
- Examples of the Kallergis/Callergi arms
- Nikolaos Panagiōtakēs/Roderick Beaton: El Greco, The cretan years, Ashgate Publishing, Ltd., 2009, p. 63 and ss.
- Sally McKee, Uncommon dominion:Venetian Crete and the myth of ethnic purity, University of Pennsylvania Press, 2000, p. 74 and ss.