I do believe that you have hit it right on the head, as this was what I was trying to reach you about, so I may as well post it here, since you have independently drawn (a more advanced, I may add) conclusion. I have some more to add that bolsters the idea.
Before I get going- Props to Charles- the Metor-Mithra-Mattan connection is simply brilliant! Call me crazy, but I think we're verging on some groundbreaking work here.
It is interesting that the Arcasids seem to have selected their throne names from the rivers in their "native" lands. Tigranes= Tigris, Phraates=Euphrates. Vonones= Volga, etc. This I believe was an exploitative association, used by the (non-persian) Arcasids to deify themselves by identifying with an already existing cult which venerated rivers (see prior post about "rus", etc.) In effect, they took the seleucids place, and the tribal fiefdoms that made up their population were almost none the wiser about it. It was about trade and tribute anyway.
Furthermore, by the time of Herod's succession (to which we wondered why the parthians were so willing to vacate their newly earned dictatorship of both State and Temple), The Parthian Arcasids "were" Roman. I have numerous citations but a would recommend a look here if your would like documentation
It has become clear from my independent study, that the Arcasid Parthian rulership was clearly not "parthian" but rather Scythian by origin (and therefore linked with Maccabee and Hyrcanian dynastic structure), with strong elements of Rome, Palestine, Greece and Egypt intertwined. It appears as if they merely supplanted the Seleucids, and the confusions that arise from questions like "where were the persians, medeanites, etc?", during the Parthian period are easily framed within this context. Like the Maccabbee and Herod lines, they were tax collectors. That's what gave them power. In the case of the Arcasids, they provided a face of local leadership, but no actual substantive links to the ancient traditions within their hegemony.
Do you remember the story of Phraates IV? Use the above link if you don't, to follow along. After conquering the three attempts by Romans to invade Parthia, Caesar Augustus and Phraates IV agree to a truce. Phraates retuned the Roman Legion Standards which were captured. Their return to Rome was listed among Augustus' Major triumphs.
(which you may read about here: http://classics.mit.edu/Augustus/deeds.html)
Rather than immediately return Tiradates (the father of Tiridates II: Gnaus Piso's best friend and schoolmate of both Tiberius' son Druces, and Caligula), he gives PhraatesIV a "slave girl" named Muses. Phraates subsequently marries 'muses', and she becomes his queen and co-regnant. Her as a gift to PhraatesIV (who despite modern notions of romantic love would never in a million years either marry a slave girl or make a non-royal his queen) was the typical way in which cooperative dynasties cemented their pacts.
In a remarkable parallel to the life of Herod (their lives and reigns overlap to the year, and they both had major wives of distinctly foreign extraction- (Herod had Cleopatra and Malthace)), she then sends her sons to Rome to be educated, and while they are abroad, she kills PhraatesIV (her husband of many years) and all the rival princes to her sons. She is then co-regnant with two of her sons, who have short reigns. Then her son Vonones enters the scene as a true monarch. Vonones has difficulties being accepted by his people, as he was clearly identified by his people as a Roman, both in style and substance.
Those who have "eyes to see", will realize that I have already said a mouthful.
But it gets better- Muses' real name (which was a bitch to find I might add), was....... Tethmuses.
I assert that Tethmuses was none other than a female offspring of Cleopatra and Mark Antony!
Mark Antony invited Cleopatra to **Tarsus** (yep), in the year 41 B.C. They had already met in 46 B.C. when Caesar brought Cleopatra to Rome. During that visit, Antony had also fallen in love with her. Because Antony had eventually wanted to become the sole ruler of Rome, he hoped to get some form of aid from Cleopatra and her people.
A year later, in 41 B.C., Cleopatra gave birth to his twins. Their history, unlike that of Caesarion, her son with Julius Caesar, has never been attested or documented other than that they were born. But even through all this, Antony had to returned to Rome in order to marry the sister of Octavius, Octavia. He did this in order to gain some degree of power in Rome.
It now becomes clear as to why this dynastic exchange might have taken place. Rome was a safe place for Parthian heirs, and Parthia a safe place for Romans- but neither egypt nor rome would have been safe for Thethmuses and her sister (I'll give you a high five if you guess who I think it is- or perhaps a 'fleur de lis' (Go Ron!).
During the war between Octavian and Mark Antony, these children were probably kept secret. Later, after Tiberius' succession, the progeny were no longer a dynastic threat to Tiberius' sons, and therefore safe to "donate" to Parthia to cement an alliance. The reason is probably because both twins were girls. As soon as Druses was born, they were safe. Having a combination of both Roman and Egyptian royal lines on the female side would give both the Herodians (oops, did I say that?) and the Arsacids an unquestioned international "right to rule" for their sons within the context of the Roman Empire. No Julio-Claudian ever tried to attack Parthia again.
Chances are Vespasian didn't know this story!
I've taken this alot further. But I want to hear what you think so far!
© Charles N. Pope, US Library of Congress. All rights reserved.