How Were Julius Caesar and His Successor Augustus Related?

Augustus Caesar was the first true Roman Emperor

A statue of Julius Caesar
Jule_Berlin / Getty Images

Augustus, known as Caesar Augustus or Octavian, was the Roman emperor Julius Caesar's great-nephew whom he adopted as his son and heir. Born Gaius Octavius on September 23, 63 BCE, the future Augustus was distantly related to Caesar. Augustus was the son of Atia, the daughter of Julius Caesar's sister Julia the Younger (101–51 BCE), and her husband Marcus Atius, the son of Octavius, a relatively average praetor from the Roman colony of Velitrae.

Key Takeaways: Augustus and Julius Caesar

  •  Julius Caesar and Augustus Caesar were distantly related, but Julius needed an heir and legally adopted Augustus as that heir in his will, which became known and in effect when Caesar was assassinated in 43 BCE. 
  • It took more than 25 years for Augustus to establish himself as Caesar's heir and take complete and lasting control of Rome, when he became Imperator Caesar Augustus on January 16, 17 BCE.
  • Augustus surpassed his great-uncle Julius in power and longevity, establishing the beginning of the Pax Romana, founding the Roman Empire to last for nearly 1,500 years. 

Augustus (63 BCE–14 CE), a fascinating and controversial man, may have been the most important figure in Roman history, surpassing his great-uncle Julius in longevity and power. It was during Augustus' long life that the failing Republic was converted to a Principate that would endure for centuries.

Why Did Julius Caesar Adopt Gaius Octavius (Octavian)?

By the middle of the first century BCE, Julius Caesar desperately needed an heir. He had no son, but he did have a daughter, Julia Caesaris (76–54 BCE). Although she was married several times, the last time to Caesar's longtime rival and friend Pompey, Julia only had one child, who died at birth with her mother in 54 BCE. That ended her father's hopes for an heir of his own direct blood (and incidentally ended the possibility of a truce with Pompey).

So, as was common in ancient Rome then and later, Caesar sought his closest male relative to adopt as his own son. In this case, the lad in question was young Gaius Octavius, whom Caesar took under his own wing in the final years of his life. When Caesar went to Spain to fight the Pompeians in 45 BCE, Gaius Octavius went with him. Caesar, arranging the schedule in advance, named Gaius Octavius his primary lieutenant or Magister Equitum (Master of the Horse) for 43 or 42 BCE. Caesar was assassinated in 44 BCE and in his will officially adopted Gaius Octavius.

Julius Caesar may have named his great-nephew Octavius as heir before he was assassinated, but Octavius did not learn of that until Caesar's death. Octavius took the name Julius Caesar Octavianus at this point, thanks to the encouragement of Caesar's own veterans. He went thereafter by C. Julius Caesar Octavianus or Octavian (or simply Caesar) until he was named Imperator Caesar Augustus on January 16, 17 BCE.

How Did Octavian Become Emperor?

By taking his great-uncle's name, Octavian also assumed Caesar's political mantle at the age of 18. While Julius Caesar was, in fact, a great leader, general, and dictator, he was not an emperor. But he was in the process of instituting major political reforms to reduce the power of the Senate and increase his own when he was assassinated by Brutus and other members of the Roman Senate.

At first, being the adopted son of the great man Julius Caesar meant little politically. Brutus and Cassius, the men who headed the faction that had killed Julius Caesar, were still in power in Rome, as was Caesar's friend Marcus Antonius (better known to modernity as Marc Antony).

Augustus and the Triumvirates

It took several years for Augustus to consolidate his position, as Julius Caesar's assassination led to an assumption of power by Antony. It was Cicero's support of Octavian—a power play in which Cicero intended to use to split Caesar's heirs—that led to the repudiation of Antony and ultimately, to Octavian's acceptance in Rome. While Octavian then had the support of the Senate, he was still not immediately made dictator or emperor. 

Despite Cicero's machinations, in 43 BCE, Antony, his supporter Lepidus, and Octavian formed the Second Triumvirate (triumviri rei publicae constituendae), a pact that would last for five years and end in 38 BCE. Without consulting the Senate, the three men divided the provinces among themselves, instituted proscriptions, and (at Philippi) fought the liberators—who then committed suicide.

The second term of the triumvirate ended at the end of 33 BCE, and by that time, Antony had married Octavian's sister and then repudiated her for his beloved Cleopatra VII, Pharaoh of Egypt.

The Battle for the Control of Rome 

Accusing Antony of setting up a power base in Egypt to threaten Rome, Augustus led Roman forces against Antony to battle for the control of Rome and the legacy Caesar left behind. Octavian and Marc Antony met at the Battle of Actium, where the fate of Rome was decided in 31 BCE. Octavian emerged victoriously, and Antony and his love Cleopatra both committed suicide. 

But it still took many more years for Octavian to establish himself both as emperor and as the head of the Roman religion. The process was complex, requiring both political and military finesse. On the face of things, Augustus restored the Republic, calling himself Princeps Civitas, the First Citizen of the State, but in reality, maintained his status as military dictator of Rome.

With all Octavian's strong opponents dead, the civil wars ended, and soldiers settled with the wealth acquired from Egypt, Octavian—with universal support—assumed command and was consul every year from 31–23 BCE.

Augustus Caesar's Legacy

On January 16, 17 BCE, C. Julius Caesar Octavianus or Octavian (or simply Caesar), finally shed his previous name and became emperor of Rome as Imperator Caesar Augustus.

A savvy politician, Octavian had even more of an impact on the history of the Roman Empire than did Julius. It was Octavian who, with Cleopatra's treasure, was able to establish himself as emperor, effectively ending the Roman Republic. It was Octavian, under the name Augustus, who built the Roman Empire into a mighty military and political machine, laying the groundwork for the 200-year Pax Romana (Roman Peace). The Empire as founded by Augustus lasted for almost 1,500 years.


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Gill, N.S. "How Were Julius Caesar and His Successor Augustus Related?" ThoughtCo, Apr. 5, 2023, Gill, N.S. (2023, April 5). How Were Julius Caesar and His Successor Augustus Related? Retrieved from Gill, N.S. "How Were Julius Caesar and His Successor Augustus Related?" ThoughtCo. (accessed June 5, 2023).