We may yet get lucky and some 'new' (well, new to us) sources emerge. The emperor Augustus had many descendants via his daughter Julia, and even Tiberius, Caligula, and Nero's best efforts to thin out the hordes of their imperial cousins couldn't kill them all.
Likewise, Mark Antony left many descendants both in the Roman upper aristocracy and abroad; his daughter by Cleopatra married the king of Numidia and they likely had descendants via that line. Perhaps some future archaeologists in Algeria, Tunisia, and Libya will turn up forgotten documents that will shed some light on them.
Probably the best DFA (descent from antiquity) is not through Rome, but via Armenia. Genealogist Stewart Baldwin has made some plausible arguments for descent from a cadet branch of the Arsacid dynasty into the later Armenian kings. The Arsacids were an Iranic dynasty and likely were descended from the even earlier Achaemenids (who had been conquered by Alexander the Great in 330 BCE).
