The Julii Caesares were the most illustrious family of the patrician gens Julia. The family first appears in history during the Second Punic War, when Sextus Julius Caesar was praetor in Sicily. His son, Sextus Julius Caesar, obtained the consulship in 157 BC; but the most famous descendant of this stirps is Gaius Julius Caesar, a general who conquered Gaul and became the undisputed master of Rome following the Civil War. Having been granted dictatorial power by the Roman Senate and instituting a number of political and social reforms, he was assassinated in 44 BC. After overcoming several rivals, Caesar's adopted son and heir, Gaius Julius Caesar Octavianus, was proclaimed Augustus by the senate, inaugurating what became the Julio-Claudian line of Roman emperors.
The first of the Julii Caesares to appear in history was Sextus Julius Caesar, praetor in Sicily in 208 BC. From the filiation of his son, Sextus, "Sex. f. L. n.", we know that his father was named Lucius, but precisely who this Lucius was and whether he bore the surname Caesar is uncertain. On the assumption that the Caesares were descended from earlier notable families of the Julia gens, some scholars have suggested that he was the son of Lucius Julius Libo, consul in 267 BC.
The Dictionary of Greek and Roman Biography and Mythology says this of the cognomen Caesar:
It is uncertain which member of the Julia gens first obtained the surname of Caesar, but the first who occurs in history is Sextus Julius Caesar, praetor in BC 208. The origin of the name is equally uncertain. Spartianus, in his life of Aelius Verus, mentions four different opinions respecting its origin:
- That the word signified an elephant in the language of the Moors, and was given as a surname to one of the Julii because he had killed an elephant.
- That it was given to one of the Julii because he had been cut (caesus) out of his mother's womb after her death; or
- Because he had been born with a great quantity of hair (caesaries) on his head; or
- Because he had azure-colored (caesii) eyes of an almost supernatural kind.
Of these opinions the third, which is also given by Festus, seems to come nearest the truth. Caesar and caesaries are both probably connected with the Sanskrit kêsa, "hair", and it is quite in accordance with the Roman custom for a surname to be given to an individual from some peculiarity in his personal appearance. The second opinion, which seems to have been the most popular one with the ancient writers, arose without doubt from a false etymology. With respect to the first, which was the one adopted, says Spartianus, by the most learned men, it is impossible to disprove it absolutely, as we know next to nothing of the ancient Moorish language; but it has no inherent probability in it; and the statement of Servius is undoubtedly false, that the grandfather of the dictator obtained the surname on account of killing an elephant with his own hand in Africa, as there were several of the Julii with this name before his time.An inquiry into the etymology of this name is of some interest, as no other name has ever obtained such celebrity — "clarum et duraturum cum aeternitate mundi nomen." It was assumed by Augustus as the adopted son of the dictator, and was by Augustus handed down to his adopted son Tiberius. It continued to be used by Caligula, Claudius, and Nero, as members either by adoption or female descent of Caesar's family; but though the family became extinct with Nero, succeeding emperors still retained it as part of their titles, and it was the practice to prefix it to their own name, as for instance, Imperator Caesar Domitianus Augustus. When Hadrian adopted Aelius Verus, he allowed the latter to take the title of Caesar; and from this time, though the title of Augustus continued to be confined to the reigning prince, that of Caesar was also granted to the second person in the state and the heir presumptive to the throne.
Outside of the Imperial family, the last of the Julii known to have borne the surname of Caesar was Lucius Julius Caesar, who had been consul in 64 BC, and who was still living in BC 40. Although other members of the family may have lived after this time, none seem to have achieved sufficient prominence to be recorded in subsequent generations.
The genealogy of the Julii Caesares was studied by Wilhelm Drumann in his monumental history of Rome, and the following tables are based largely on his reconstruction of the family. In most respects, Drumann's genealogy forms the basis for modern scholarship on the family, with one important exception: Drumann believed that the Sextus Julius Caesar who was a military tribune in 181 BC and the Sextus who was consul in BC 157 were father and son. While chronology suggested that the tribune might be the son of the Sextus who had been praetor in 208 BC, the consul's filiation indicated that his grandfather's name was Lucius. Accordingly, Drumann inferred the existence of an otherwise unknown Lucius Julius Caesar between the praetor and the military tribune, although in order to make sense chronologically, the praetor would have to have been rather elderly and the tribune very young when they held their respective offices. More recent scholarship has concluded that the military tribune and the consul were the same man, which means that his grandfather, Lucius, was the father of the praetor of 208 BC, rather than his son.
It is therefore Sextus, the praetor of BC 208, rather than an otherwise unknown Lucius Julius Caesar, who was the father of Lucius Julius Caesar, praetor in 183 BC, and Sextus, the consul of 157. These sons provide the first two branches of the family; but the third branch, representing the ancestors of Gaius Julius Caesar, the dictator, are less certain. We know that Caesar's grandfather was also named Gaius, and that he married a woman of the Marcia gens. Drumann supposed that he might have been the son of a senator named Gaius Julius, who wrote a Roman history in Greek about BC 143. This Gaius, he proposed, might have been a brother of Sextus Julius Caesar, the consul of 157, and therefore a son of the Sextus who was military tribune in 181. Since the two Sexti were in fact the same man, this would probably make the senator Gaius a third son of Sextus Julius Caesar, the praetor of 208 BC. If he was a senator in 143, and the great-grandfather of Caesar, who was born in BC 100, he was probably not the consul's son, as his eponymous and presumably eldest son, Sextus, was praetor in BC 123.
The rest of the genealogy is well-known. As Caesar left no legitimate sons to carry on his name and legacy, by his will he adopted his grand-nephew, Gaius Octavius, who thus became Gaius Julius Caesar Octavianus, the future emperor better known as Augustus. Octavian had only a daughter, and therefore adopted two of his grandchildren by Marcus Vipsanius Agrippa, who thus became Gaius and Lucius Julius Caesar; but when both died young, the emperor adopted their brother, who became Marcus Julius Caesar Agrippa Postumus, and a stepson, Tiberius Claudius Nero, who became Tiberius Julius Caesar. Tiberius' son, Nero Claudius Drusus, became Drusus Julius Caesar, and he adopted a nephew, Tiberius Claudius Nero Germanicus, who became Germanicus Julius Caesar; their children also became part of the Julia gens. The line draws to a close with the death of Germanicus' son, Gaius Julius Caesar Germanicus, better known simply as Gaius or Caligula, in AD 41; after this, the imperial authority passed to Gaius' uncle, Tiberius Claudius Nero Germanicus, and out of the Julian line.
The table below reflects known and probable relationships, with speculative descent indicated by a question mark "(?)".
The male line of the family, showing both natural and adoptive lineage through the Julio-Claudian emperors.