Polibius was a cultured Greek exiled in Italy, who became the friend/tutor of the Fabius and Scipio (pic) brothers. With their father still in life, they were adopted by two different senatorial families who had no male successors. Two other brothers were left to continue their biological family's line (but they died soon so their own family name disappeared). It appears that the Roman upper class was almost childless, which Polibius attributes to moral decay. He also mentions the sudden depopulation of his own Greece, and how it came suddenly upon them. From V. Day:
About the fate of the Roman upper class: Among European peoples, the Romans offer an especially useful example because they left masses of records, enabling later historians to determine what became of them. The evidence found in ancient texts implies that this class descended largely from people who had a decidedly northern European physical type, although that isn't something one reads in modern books about Roman history. In Rome, though, the upper class was always a tiny minority. Instead of protecting its interests, it allowed itself to wither away. Consider a bleak statistic. We know of about fifty patrician clans in the fifth century B.C., but by the time of Caesar, in the later first century B.C., only fourteen of these had survived. The decay continued in imperial times. We know of the families of nearly four hundred Roman senators in A.D. sixty-five, but, just one generation later, all trace of half of these families had vanished.Polybius's carrier and History is parallel to Favius Josephus' The Jewish Wars, both dedicated to improve the image of their newly conquered peoples among the Romans. Both dedicate extraordinary effort to combat fellow historians. Polybius dedicates a third of his book to slander and to ridicule one Thimaeus.