His father made him Marshal in 1138, due to the invasion of John II Comnenus, and escaped capture by sheltering in Edessa. In 1157, he began raiding Byzantine territories around Marash against his half-brother Thoros' will, although he failed to capture Marash itself. The Byzantine governor of Tarsus, Andronicus Euphorbenus, invited him to a banquet. Stephen's corpse was found the next day and it was believed Andronicus murdered him. Thoros avenged his death with a massacre of Greeks within his territories, which would have led to war had not Amalric I of Jerusalem intervened to bring about a peace.
He had at least three children by his wife Rita of Barbaron:
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- Runciman, Steven (1989). A History of the Crusades, Volume III: The Kingdom of Acre and the Later Crusades. Cambridge University Press.