In c.105 CE, the Parthian king Pacorus II died. Vologases I died. He was succeeded by his brother Osroes I, who inherited a conflict in the eastern part of the Parthian Empire, where Vologases III had revolted, the son of Vologases II, a rebel of Pacorus' early days.
Little is known about this conflict, except for the fact that Vologases' coinage continued for more than forty years. He survived Osroes, who died in 129, and continued to rule during the reign of Osroes' successor Mithradates V (r.129-147). The civil war must have been an endlessly smouldering conflict, partly because Osroes never could fight against his rival: the war against the Roman emperor Trajan, which lasted from 114 to 117, demanded all his attention.
After the war against Rome, Osroes had lost control of his northern zone of influence in Armenia. The Romans allowed Vologases III to occupy this country, which was, after all, usually ruled by an Arsacid. This turned out to be a poisoned gift, because it made him vulnerable to attacks from the northern tribe of the Alans. At a later stage, an Armenian king named Pacorus appears to have succeeded him.
From coins, we can deduce that there briefly was another, unidentified king in about 140. After 147, Vologases did not mint any coins, and we can assume that the empire had been reunited by Vologases IV, the son and successor of of Mithradates V.
The chronology of the Arsacid kings of the Parthian Empire is less well-understood than, for example, the sequence of Seleucid and Ptolemaic kings or the emperors of Rome. This information is based on the researches by G.R.F. Assar, as published in "Iran under the Arsakids, 247 BC – AD 224/227" in: Numismatic Art of Persia (2011).