Of the lineage and names of the Porcian family.

When Sulpicius Apollinaris and I, with some others who were friends of his or mine, were sitting in the library of the Palace of Tiberius, it chanced that a book was brought to us bearing the name of Marcus Cato Nepos. We at once began to inquire who this Marcus Cato Nepos was. And thereupon a young man, not unacquainted with letters, so far as I could judge from his language, said: "This Marcus Cato is called Nepos, not as a surname, but because he was the grandson of Marcus Cato Censorius through his son, and father of Marcus Cato the ex-praetor, who slew himself with his own sword at Utica during the civil war. There is a book of Marcus Cicero's about the life of the last-named, entitled Laus Catonis, or A Eulogy of Cato, in which Cicero says 65 that he was the great-grandson of Marcus Cato Censorius. Therefore the father of the man whom Cicero eulogized was this Marcus Cato, whose orations are circulated under the name of Marcus Cato Nepos."
Then Apollinaris, very quietly and mildly, as was passing his custom when passing criticism, said: "I congratulate you, my son, that at your age you have been able to favour us with a little lecture on the family of Cato, even though you do not know who this Marcus Cato was, about whom we are now inquiring. For the famous Marcus Cato Censorius had not one, but several grandsons, although not all were sprung from the same father. For the famous Marcus Cato, who was both an orator and p465a censor, had two sons, born of different mothers and of very different ages; since, when one of them was a young man, his mother died and his father, who was already well on in years, married the maiden daughter of his client Salonius, from whom was born to him Marcus Cato Salonianus, a surname which he derived from Salonius, his mother's father. But from Cato's elder son, who died when praetor-elect, while his father was still living, and left some admirable works on The Science of Law, there was born the man about whom we are inquiring, Marcus Cato, son of Marcus, and grandson of Marcus. He was an orator of some power and left many speeches written in the manner of his grandfather; he was consul with Quintus Marcius Rex, and during his consulship went to Africa and died in that province.
But he was not, as you said he was, the father of Marcus Cato the ex-praetor, who killed himself at Utica and whom Cicero eulogized; nor because he was the grandson of Cato the censor and Cato of Utica was the censor's great-grandson does it necessarily follow that the former was the father of the latter. For this grandson whose speech was just brought to us did, it is true, have a son called Marcus Cato, but he was not the Cato who died at Utica, but the one who, after being curule aedile and praetor, went to Gallia Narbonensis and there ended his life. But by that other son of Censorius, a far younger man, who, as I said, was surnamed Salonianus, two sons were begotten: Lucius and Marcus Cato. That Marcus Cato was tribune of the commons and died when a candidate for the praetorship; he begot Marcus Cato the ex-praetor, who committed suicide at Utica during the civil war, and when Marcus Tullius wrote the latter's life and panegyric he said that he was the great-grandson of Cato the censor. You see therefore that the branch of the family which is descended from Cato's younger son differs not only in its pedigree, but in its dates as well; for because that Salonianus was born near the end of his father's life, as I said, his descendants were considerably later than those of his elder brother. This difference in dates you will readily perceive from that speech itself, when you read it."
Thus spoke Sulpicius Apollinaris in my hearing. Later we found that what he had said was so, when we read the Funeral Eulogies and the Genealogy of the Porcian Family.

Attic Nights, by Aulus Gellius. Book XIII. 20