Mithridates
The Mithridates who became king of Armenia in 36 CE, was a younger son of another Mithridates, who had been king of the West-Caucasian kingdom of Iberia (modern Georgia) during the reign of the emperor Augustus. This earlier Mithridates had been succeeded by his eldest son, crown prince Pharasmanes I. This family descended from the old dynasty of Armenia, the Artaxiads.note
In Armenia itself, the Artaxiad line had come to an end at some point after 6 CE; in 18 CE the Roman prince Germanicus had appointed Artaxias III Zeno, a Pontic prince, as king of Armenia. After his death, the Parthian king Artabanus II (r.10-38) had intervened and had made his son Arsaces king in Armenia (34 CE). This was an interference in the affairs of the Roman Empire, because it was the Roman emperor who was supposed to appoint Armenian kings.
As a countermeasure, the Roman governor in Syria, Lucius Vitellius, invited the younger Mithridates to seize the Armenian throne. The result was a full-scale war between the pro-Parthian Armenians and the Iberians, who captured the Armenian capital Artaxata.{Tacitus, Annals 6.33.}} When king Artabanus of Parthia sent troops to intervene on behalf of Arsaces, the Iberians invited Sarmatian nomads from Central Eurasia.note Artabanus now wanted to intervene personally but Vitellius ordered his legions (III Gallica, VI Ferrata, X Fretensis and XII Fulminata) to prepare for war (late 35?) and supported a pretender in the Parthian Empire, Tiridates II. This forced Artabanus to accept the pro-Roman Mithridates of Iberia as the new king of Armenia.note
He was to govern Armenia from 36 to 51 CE, supported by his brother Pharasmanes and a Roman garrison. He was briefly detained in Rome by Caligula but released by Claudius. Towards the end of Mithridates' reign, he was replaced by his nephew, Rhadamistus, son of Pharasmanes.note