Nothing is known about the activities of the Siwnis prior to the Christianization of Armenia in the early fourth century. The Siwnis participated in the Christianization and a Siwni prince accompanied Gregory the Illuminator to Caesarea to be ordained Patriarch of Armenia. The first Siwni prince whose name we know is Vaghinak Siwni, who was appointed of Arzanene by King Khosrov III. Vaghinak's brother Andok or Andovk became an important military commander in the late 330s. In the mid-fourth century, King Tiran appointed Pʻisak Siwni commander of the eastern part of the Armenian troops, while Andovk was made overseer of Arzanene and the city of Tigranocerta. After Vaghinak's death, Andovk became the head of the Siwni dynasty. His influence and authority increased after King Arshak II married his daughter Parandzem. Andovk was a member of the pro-Roman faction of Armenian magnates. He commanded the defense of Tigranocerta against the invading Sasanian king Shapur II in the mid-360s. After the occupation of Armenia by Shapur, Siwnikʻ was ravaged by the Persian troops and many members of the Siwni family were hunted down and killed.
