Different texts identify the various Hasmonean and Herodian princes differently. On this site, I use the convention that only proper kings are given the suffix I, II, III, IV, etc. For example, the princes named Aristobulus that did not become king are instead identified by the names of their father, mother, or some other relation. My Aristobulus III is then the husband of "tiny dancer" Salome. The Aristobulus that was "accidentally" drowned had briefly become High Priest, but never king, so I don't refer to him with a Roman numeral. This Aristobulus would have died about the same time as Caesarion and was about the same age. We think that the two may actually have been one and the same.
Regarding the kings named Tigranes, there is a definite parallel between the two that were contemporary with Julius Caesar and the two that were contemporary with Nero Caesar. The second Tigranes of the earlier period we have associated with Octavius II/Antigonus II (Caesar Augustus). Therefore, the royal prince designated as the second Tigranes in the reign of Nero was effectively designated (by association) as a potential successor of Nero! That prince was Aristobulus III, and there is now reason to conclude that the kings starting with Nerva were in fact the descendants of Aristobulus III.
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