constantine was a nephew of the powerful michael keroularios, patriarch of constantinople in 1043–1059. the name of his father is unknown. a friend and correspondent of michael psellos, constantine and his brother nikephoros were among the supporters of isaac i komnenos when he rose in revolt to seize the throne in 1057, and went on to occupy senior offices in the byzantine hierarchy. in his correspondence with psellos, constantine is variously referred to by the high court ranks of "sebastos", "proedros", "protoproedros", and "magistros", the senior fiscal offices of "sakellarios" and "genikos logothetes", and the judicial offices of "epi ton kriseon" and "droungarios tes viglas". it was probably under constantine's tenure that the latter office acquired the epithet ""megas"" ("grand"), and was confirmed as the empire's senior-most judicial authority. constantine was apparently also the first person to hold the title of "sebastos". a seal which may be attributable to him further records the titles of ""vestarches", judge of the velum, and grand curator of the mangana".