Adiabene in the Talmud is called Hadayb and is identified with Habor of II Kings 17:6 in Kddushin 17a. Where some of the Northern Kingdom exiles were transported.
Josephus records how Helena the wife of Adiabene's king Monobaz I converted to Judaism, around the same time so did her son Izates. A Jew named Ananias was their teacher in Judaism. Izates and Monobaz II his older bother both ruled the Kingdom. Izates died before 60 AD. Monobaz II assisted the Jewish rebellion against Rome in 66-70 AD, we know nothing about his fate or history after 70 AD, or indeed the Kingdom at all till the reign of Trajan. Helena and Izatez were buried in Jerusalem.
The Yosippon (a not easily available in English Hebrew adaptation of various parts of Josephus, but could also relate some useful independent information), claims that both Agrippa II and Monobaz II were killed by Rome in the 66-73 AD War. Because Agrippa II we know lived after that, the entirety of that reference is often considered discredited. But Monobaz fate is unknown, the Romans didn't usually let people who rebelled against them get off easy (Agrippa was on their side so they wouldn't kill him). And it's not hard to imagine reasons Josephus wouldn't have mentioned Monobaz being executed.
However if Monobaz did die during that War I doubt it was at it's start as the Yosippon actually says, placing it 1290 days before the Temple's destruction on the 9th of Av in 70 AD. The text of Yosippon wants to present this double murder as fulfilling the Messiah being Cut Off of Daniel 9, which is why Preterists love quoting it. In Josephus Menahaim ben Judas the Galilean was killed about this time after being Crowned.
If Izates and Monobaz were descendants of Northern Kingdom Exiles who had lost their identity, but now had returned to Yahweh worship and lead their entire nation in doing so. And if Monobaz II died in battle with Edom in 70 AD. It's interesting how they resemble the role that Messiah Ben-Joseph is expected to play by modern Jews. All that would be left is for one or both of them to be Resurrected by Messiah Ben-David.
Josephus' biography of Izates even tells us his paternal half brothers were jealous of him because of the favoritism he received being the son of the favorite wife. So his story has parallels to Joseph.
What's interesting about that to me is that there is also speculation that the Judaizm they converted to may have been early Christianity. The fact that whether or not Izates should be circumscribed is a source of disagreement is interesting. The Ananias they knew has been speculated to be the Ananias of Acts. And according to Moses of Khorone, Helena later married the Christian King Abgar of Osroene (Osroene's capital was Edessa), another Mesopotamian region, after her first husband Monobaz I died.
Monobaz II is quoted in the Talmud as saying something possibly influenced by Jesus.
"My fathers stored up below and I am storing up above... My fathers stored in a place which can be tampered with, but I have stored in a place which cannot be tampered with… My fathers gathered treasures of money and I have gathered treasures of souls."-Baba Batra 11a.Matthew 6:19-21
"Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal: But lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal: For where your treasure is, there will your heart be also."It'd be interesting if Helena, Izates II and Monobaz II are all resurrected at The Rapture and proclaim Jesus to be The Messiah Ben-David to all who witness it.
Assyrian Christian traditions say Thomas, Thaddeus and Bartholomew were the first to bring the Faith to Assyria. And that Peter was in Babylon like he said he was when he wrote 1 Peter. But the details of the early development of Mesopotamia Christianity are not well documented. Their first known Bishop was from the time of Trajan.
The majority of Assyrians were Christians already when Constantine made it legal in Rome, and so they defected to Rome from Persia.
Many scholars believe the royal family of Adiabene could be among the ancestors of the Amatuni, a noble family that popped up in Armenia in the fourth century, and were Christians.
If the Amatuni could be from a family with Jewish stock, I feel that gives credibility to the claims of the Bagartid dynasty, who shows up near the same region only a century or two later.
What is interesting about the Bagratid claim is they claim to come from the near Kin of Jesus.
The descendants of Jesus half siblings, or at least some of them, remained in Jerusalem and were pretty much the exclusive leadership of the Jerusalem church til the Bar-Kochba revolt. They didn't disappear entirely then however.
Eusebius quotes Julius Africanus as referring to people claiming to be descended from the siblings of Jesus in his day, but they had now left Judea and traveled into other countries.
A few of the careful, however, having obtained private records of their own, either by remembering the names or by getting them in some other way from the registers, pride themselves on preserving the memory of their noble extraction. Among these are those already mentioned, called Desposyni, on account of their connection with the family of the Saviour. Coming from Nazara and Cochaba, villages of Judea, into other parts of the world, they drew the aforesaid genealogy from memory and from the book of daily records as faithfully as possible.I think Sumbat's Chronicle is corrupted and confused by the early traditions that were uncomfortable with Jesus having siblings by the same mother.
Genealogy of the Bagrationi dynasty according to SumbatGeneration 60 has Cleopas which I believe the original source of the genealogy probably had Joseph. And I also think his and Jacob's spots got switched. That makes Naom, generation 62, the same generation as Jesus. Now you may be thinking, Jesus didn't have a brother named Naom?
The male name Naom is a fairly rare Hebrew name, I don't think anyone in The Bible had it in either Testament. But it's feminine form, Naomi, is infamous as the name of an important character in the book of Ruth, about the origins of the Davidic Line.
We don't know the names of Jesus sisters, maybe one was named Naomi? But later record keepers wanted to obscure that they'd carried this line through a woman.
We know the identity of one of Izates's wives and she wasn't from Judea but another Proselyte. But Josephus says he had 48 children in 25-30 years. So clearly he had more wives. First century Judaism was still practicing Polygamy. We also don't know if Monobaz II ever married or reproduced at all.
Two early second century Rulers of Osroene were called "Bar Ezad"(Son of Ezad) even though no ruler named Ezad is mentioned. It could be this indicates further ties between Izates and the family of Abgar. Abgar bar Ezad also rebelled against Trajan when the Jews of the region did. Agbar VIII and Agbar IX were probably descended from Manu Bar Ezad.
Moses of Khorone clearly felt the people of Abgar's Edessa were among the progenitors of the Armenians of his day which is why he focused on Agbar so much and not on the actual rulers of First Century Armenia who were always either Roman or Parthian vassals.
Creating a Jewish monarchy Izates and Monobaz could very likely have sought descendants of David as wives. And if they were early Christians, could have desired strong ties to Jesus family who were leading the Jerusalem Church and probably other early Jewish-Christian Churches as well.
The Kingdom of Osroene was also founded by Nabateans in the second century BC, making them Ishmaelites.
Modern DNA studies have shown that modern Jews are close cousins to Armenians and Christian Kurds.
Update April 2016: These theories happened to come up in my discussion of Arthurian Legend and Grail Romances.