Tiberius (69) - still Emperor of Rome, unofficially retired at CapriGot all that? Great! Now, the list of ancient sources: Tacitus' Annals 4.68-70 & 5.3.1, Suetonius' Caligula 10.1, Dio Cassius 58.1.1-3, Pliny's Natural History 8.145, and Velleius Paterculus 2.130.4-5, plus a couple of inscriptions. Barrett also lists an extensive bibliography of scholarship on the controversy, which we might say essentially boils down to one question - When was Agrippina banished?
Livia (85) - Tiberius' mom, Augustus' widow, Agrippina's step-grandmother but Germanicus' biological grandmother, and so also great-grandmother of Agrippina's children
Germanicus (dead ten years) - Tib's nephew and adopted son, Liv's grandson, Agrippina's husband (the couple themselves were of no blood relation)
Agrippina (41) - 'Agrippina the elder' - widow of Germanicus, Aug's granddaughter, Livia's step-granddaughter, Tiberius' neice-in-law (formerly also daughter-in-law), mother of Nero (22, not the future Emperor) and Caligula (16, yes the future emperor)
Sejanus (40's?) - Tiberius' Praetorian Prefect and all around proxy ruler in Rome
As a last point of reference, understand that Sejanus was not necessarily trying to become Emperor himself, but his immediate aim was definitely to remain as the power behind the throne. That, precisely, is why Agrippina herself was Sejanus' chief obstacle. Obviously, at least one of her children was poised to succeed the rapidly aging Tiberius. Livia and Agrippina were hardly close allies, but both women supported the children. That's the thick of the plot.
Okay, now to the sources... and thus to the controversy.
Tacitus says that when Livia died, Sejanus took that opportunity to publicly denounce Agrippina and Nero (her oldest; a middle son, the 3rd Drusus of this era, now age 21, was supporting Sejanus' attack on his mother and brother). The Senate responded by banishing them to the island of Pandateria. Note well: this puts Agrippina's banishment firmly after Livia's death.
Suetonius, however, says that Caligula went to live with his great-grandmother Livia after Agrippina's banishment. Thus, how could Livia be dead before this banishment? The simplest solution is that there were two banishments. But is this at all likely? Fortunately, we don't have to judge. We have further evidence.
Pliny speaks of the trial of one Titius Sabinus, a friend of Germanicus' family. Sabinus was convicted and executed of something treasonous, but that's not the story here. Pliny mentions that Sabinus' trial "came about ex causa Neronis - as a consequence of Nero's case". Barrett continues:
Because the trial of Sabinus belongs to 28, Nero must have been charged at least by that date and thus before Livia died... the most satisfactory explanation is probably [that] Sejanus' attack was broken into two stages...Barrett concludes the 'banishment' (ea relegata) mentioned by Suetonius must be a phrase used loosely to refer to a house arrest at Herculaneum, probably in 28, before the final banishment from the mainland was pronounced in 29. Suetonius' narrative, says Barrett, "is very condensed at this point" and "events might well have been telescoped". (A phrase that reminds me emphatically of Luke 2:1-5, but now I digress.) Finally, we also note that Velleius Paterculus, whose work was published in 30 AD, mentions on his last page the grief of the Emperor at the loss of his daughter-in-law and grandson, the sorrow of which Velleius then says "was crowned by the loss of his mother". Velleius' flattery aside, he would have no reason to twist the sequence of these three references against such a recent and well known chronology.
In summary, Agrippina was "banished" before she was actually banished.
Now, a few observations.
Barrett's two-page appendix is incredibly tight, and a masterful illustration of how to deal with such a seeming contradiction in sources. As a historian, Barrett inclines to trust his sources as far as he reasonably can. There may seem to be a trace of apologetic for Suetonius, but I would argue that Barrett's focus remains strictly on the facts. It is more likely Caligula would have needed a matron at age 15 than at any time afterward. The toga of manhood could be presented as early as age 15. (Caligula's birth date: Aug.31.0012) Suteonius has that much going for his claim, at the very least.
On a separate note, it may seem at first that Barrett has a great advantage here in his number of sources. Of course this is relatively true. At least: "One witness is no witness." On the other hand, we should note that nowhere does Barrett's argument actually appeal to or depend on the number of witnesses. It is the sheer number of facts in this case which prove most helpful to straightening out the necessary details. Had Suetonius provided the information that Pliny provided, the same conclusion should have been reached, assuming we have cause to believe Suetonius' report is trustworthy.
Finally, why am I posting all this? For two reasons.
Secondly, the story about Agrippina's fall and Livia's death helps to enhance a suggestion I made in my post on the Chronology of the Gospels. This is only a guess, but if GOD needed Herod Antipas to get out of Galilee just before Jesus began to gain serious fame, and if Livia's death (and thus the Tetrarch's need to get face time with Sejanus during the ensuing power shift) was indeed the occasion that drew Herod to Rome, then I don't mind speculating on one point. Did you notice how OLD Livia was? Queens in Antiquity often lived even longer than Kings, but 85 is getting way on up there for that day and age. Not to be superstitious - especially because it probably cannot be proven that Antipas even left Galilee at all - but if GOD was involved in the historical details around Christ's public years, it sure looks like Livia could be a female Methuselah. It's worth noting, at least.
But firstly, of course, this is a further step in my preliminary response to Tim's question on Thursday, about Nazareth, fishermen and money changers. As I then said on Friday, these are sidebar issues on which Gospel Chronology does not depend. That said, the question of their historicity is still important - though I may not get to covering these points right away. Whenever I do, however, I want it to be known that Barrett's investigation of facts and details in his sources will be my model for looking at whether it "seems likely" that Jesus had two Nazareth homecomings, had to call Peter twice (three times, actually), and whether he cleansed the Jerusalem Temple twice.
If I was a better general historian, I could probably name more examples of things that may or may not have "happened twice". I'm only guessing there are some, but in so vast a field as history, there simply must be. Barrett's happens to be one that I know of, and I daresay it's a good one.
Hopefully, this was worth putting online for many reasons. Enjoy. And stay tuned...