How the only biological son of Roman general Julius Caesar became the last pharaoh of Egypt

At age three, Caesarion, the alleged love child of Julius Caesar and Cleopatra, was already co-king of Egypt. He became his mother’s co-ruler just months after his alleged father, Julius Caesar, had been assassinated. But his rule was short-lived.

Believed to be the only biological son of the most powerful man in Rome, Caesarion was seen as a threat to Rome’s greatness, thus, his adoptive brother had him killed, shortly after the death of his mom, Cleopatra. His death at age 17 ended the Ptolemaic line of rulers that had controlled Egypt since the time of Alexander the Great.

Here’s his story.

Full name Ptolemy Philopator Philometor Caesar, also called Ptolemy XV Caesar, Caesarion’s mother, Cleopatra, was the daughter of Ptolemy XII. When Cleopatra was 18, her father Ptolemy XII named her and her 10-year-old brother Ptolemy XIII, as co-heirs. According to one account, they would serve together under the guardianship of Rome since Egypt was a Roman protectorate.

When their father died in 51 B.C., Cleopatra married her 10-year-old brother and co-ruler, Ptolemy XIII, but there was no love between the two. What’s more, Cleopatra began competing with Ptolemy XIII to rule Egypt. Ptolemy III’s advisers subsequently initiated plans to make him the sole ruler.

At the same time the two were competing for the throne, there was also a battle in Rome over who would control its mighty empire. Julius Caesar and Pompey the Great, two of Rome’s great military heroes, were engaged in a civil war  — the Battle of Pharsalus — and were in search of alliances. Pompey, who wanted Egypt to be on his side, threw his weight behind Ptolemy XIII over Cleopatra, who went into exile. She fled to Syria, set up her own base of operations and raised an army.

Julius Caesar would defeat Pompey in the Battle of Pharsalus in 48 B.C. Pompey fled to Alexandria but was executed by Ptolemy III, who presented his head to Julius Caesar while the latter was in Egypt. It was during this same period that Cleopatra sneaked into Alexandria, met with Julius Caesar, and managed to get his help in defeating her brother Ptolemy XIII.

After Ptolemy III’s death, Julius Caesar placed Cleopatra, who was then 21, on the throne. She co-ruled with a younger brother, Ptolemy XIV. At the same time, she took Julius Caesar as her lover and even invited the Roman general, who was 30 years older than she was, to stay in Egypt with her. Right after Julius Caesar left Egypt, Cleopatra was pregnant. She gave birth to Caesarion in 47 B.C. and made it known to all that Julius Caesar was the father. Sources say Julius Caesar invited Cleopatra and Caesarion over to Rome at the end of 46 B.C. There, Julius Caesar recognized Caesarion as his son, making him his only surviving child. But he didn’t acknowledge Caesarion as his heir. When he was killed in 44 B.C., his will stated that his great-nephew, Gaius Octavius (Octavian), was his heir.

Caesarion had spent the first two years of his life with his mom Cleopatra in Rome when Julius Caesar died. The two were forced to return to Egypt after his death as they feared for their lives.

Back in Alexandria, Cleopatra allegedly arranged the death of her younger brother, Ptolemy XIV, to pave the way for her son to ascend the throne. In 44 B.C., Caesarion, at just three years old, was declared Ptolemy XV, a co-king alongside his mother.

He would come to be appointed as “King of Kings” in 34 BC by Mark Antony. Antony, who was Julius Caesar’s lieutenant, had arrived in Egypt as Roman triumvir in charge of the eastern provinces. He started a love affair with Cleopatra and the two had three children. When he gave Caesarion the title “King of Kings”, he also formally recognized him as the legitimate son of Julius Caesar, incurring the wrath of the new leaders in Rome, including Octavian, who subsequently declared war on Cleopatra and Antony.

After Antony’s defeat at Actium in 31 B.C., Cleopatra sent Caesarion to Berenice, a seaport on the Red Sea coast of Upper Egypt. But while Caesarion was on his way, he learned that Roman troops had entered Alexandria and that his mother and Antony were both dead. He returned to Alexandria after his tutor suggested that he might be spared by Octavian and would be made to retake the throne. But upon his return, he was arrested and executed, following orders from Octavian.

And that was how the Ptolemaic rule in Egypt ended.