Middle Byzantine period

The Kantakouzenoi likely originated in Asia Minor; they first appear in the reign of Alexios I Komnenos, when a member of the family campaigned against the Cumans in 1094.^[3] From the 12th century onwards, their interests and properties seem to have lain more in the European provinces of the empire in mainland Greece.^[4] Like many other Byzantine families, they rose to nobility as members of the military aristocracy. Owning large estates, they became part of the social class known at the time as the dynatoi ('the powerful').^[5] In the Komnenian period, members of the family are attested as military officials: the sebastos John Kantakouzenos was a general under Manuel I Komnenos and lead many successful campaigns between 1150–1153; he was killed in the Battle of Myriokephalon in 1176.^[6] His probable grandson, the Caesar John Kantakouzenos, married Irene Angelina, the sister of Isaac II Angelos. By the time of the Fourth Crusade, the Kantakouzenoi were among the greatest landholders in the empire, possessing vast estates in the Peloponnese.^[3][7]

Late Byzantine period

John VI Kantakouzenos as Byzantine emperor.

The family remained prominent in the Palaiologan period. In the 13th century members of the family appeared in the Peloponnese and Nicaea^[6] and some of them were accepted into the elite of the Byzantine society, the hereditary aristocracy, known as eugeneis ('well-born').^[5] Michael Kantakouzenos was appointed the first epitropos (governor) of the Morea in 1308 and his son, John VI Kantakouzenos, rose to be megas domestikos, regent, and eventually emperor (r. 1347–1354).^[8] When Andronikos III Palaiologos died in 1341, his underage son John V Palaiologos (r. 1341–1391) inherited the throne. Disputes over regency were raised between two opposing aristocratic factions; on one side stood Andronikos III's friend and powerful Grand domestic John Kantakouzenos, who was proclaimed regent and was soon recognised as co-emperor by his armies. He was challenged by the self-proclaimed council of regency consisting of John V's mother and widowed empress Anna of Savoy, the Patriarch John XIV Kalekas, and megas doux Alexios Apokaukos.^[9] The disputes led to a devastating civil war lasting from 1341 to 1347 and won by John, who gained control of the capital and was formally crowned senior co-emperor as John VI.^{[10][lower-alpha 1]} Kantakouzenos attempted to consolidate his own dynasty on the imperial throne marrying his daughter Helena Kantakouzene to John V and proclaiming his son Matthew Kantakouzenos as co-emperor (r. 1353–1357). Intending to usurp the throne for himself, John V initiated a new series of civil wars from 1352 to 1357 against his co-emperors, which he eventually won; Matthew was captured and held hostage by the Serbs, who had allied with the Palaiologoi, and was eventually handed over to John V for ransom. Defeated, he was forced to resign marking the end of the imperial Kantakouzenos family (John VI had already been removed from power and retired in a monastery in 1354).^[11]

John VI's younger son Manuel Kantakouzenos remained despotes in the province of Morea from 1349 until 1380. Of John's other daughters, Maria married Nikephoros II Orsini of Epirus, and Theodora married the Ottoman bey Orhan I.^[3] The despot of Morea, Manuel, died in 1380 and was succeeded by his older brother and former co-emperor Matthew, who had travelled to Morea in 1361. In c. 1382, Theodore I Palaiologos was appointed by the emperor to be the new ruler of Morea. In 1383, upon the transition of power from the Kantakouzenos to the Palaiologos family, Matthew's son, Demetrios Kantakouzenos (perhaps along with his brother John) briefly succeeded his father as ruler of Morea and rivaled the Palaiologoi who nevertheless gained control of the province; Theodore became despot in 1383.^[12] It is generally believed that John, about whom relatively few documents have survived, died childless, and that the numerous Kantakouzenoi of the following generation, as well as the historian Theodore Spandounes and the wife of genealogist Hugues Busac, trace their descent from Matthew through Demetrios.^[13] The possible descendants of Demetrios (the exact parentage is uncertain) were Georgios, called "Sachatai"; Andronikos, the last megas domestikos of the Byzantine Empire; Irene, who married Đurađ Branković; Thomas, who served in Branković's court; Helena, who became the second wife of David of Trebizond; and an unnamed daughter, who may have become queen of Georgia.^[14]