Caesar Lyon, the last pharaoh of ancient Egypt, was born on June 23, 47 BC, in the palace of Alexandria, the capital of Egypt under the rule of the Ptolemaic dynasty. At that time, his mother Cleopatra VII was 22 years old and his father Julius Caesar was 53 years old, but they were not married, so he was an illegitimate child.

The full name of Caesar Lyon is Ptolemy Philopator Philometor Caesar (Greek: Πτολεμαίος Φιλο π άτωρ Φιλομήτωρ Καίσαρ）， Among them, "Ptolemy"（ Πτολεμαίος） It is the name of the kings (pharaohs) of the Ptolemaic dynasty, meaning "fond of war" and "revered for military force"; "Philopator"（ Φιλο π άτωρ） It is a nickname, meaning "devoted to loving one's father"; "Philomertor"（ Φιλομήτωρ） It is also a nickname, meaning "devoted to loving one's mother"; Caesar (Greek: Καίσαρ， Caesar is the name of his biological father Julius Caesar, originally meaning "thick hair.". Sometimes, he is also called Ptolemy Caesar (Greek: Πτολεμαίος Καίσαρ， Latin: Ptolemaeus Caesar, but the most commonly used is his nickname Caesar Leon (Greek: Καισαρίων， Caesarion in Latin means "little Caesar".

From Alexandria to Rome
On June 23, 47 BC, Caesar Lyon was born in Alexandria.
Queen Cleopatra publicly declared that Caesar was her son's father and hoped that Caesar would designate Lyon as the heir of the Julius family and the future leader of the Roman Republic. But Caesar refused and chose his nephew and adopted son Octavian. Caesar Lyon, on the other hand, was designated as the nominal heir to the common rulers of Egypt and Rome, as well as the East and West (referring to Cleopatra and Caesar), but this identity was in vain and disappeared with Caesar's assassination.
Caesar was assassinated. Shortly after his birth, Caesar Lyon came with his parents to the capital of the Roman Republic, Rome (now the capital of Italy). From 47 BC to 44 BC, he and his parents were both in Rome. When his father Caesar was assassinated on March 15, 44 BC, he and his mother were likely still in Rome and had personally witnessed the incident.
From Rome to Alexandria
After Caesar's assassination, the queen and her son immediately returned to Egypt. On July 26, 44 BC, the queen's younger brother, nominal husband, and co ruler Ptolemy XIV died of a malignant disease (some say he was poisoned by the queen), and the queen began to rule alone. On September 2 of the same year, the queen appointed her son Caesar Lyon as co ruler (pharaoh). In Rome, after the assassination of Caesar, the adopted house and the peacekeeping forces formed a rear three headed alliance with Mark Antony and Leipida, eliminating the common enemy of the republican faction and dividing the highest power of the republic. After excluding Lepida, Octavian even married his sister Octavian in order to win over Antony and let him rule the eastern territory of the Republic. But in 42 BC, Antony and the Queen met in Tarsus and, like Caesar, were enchanted by the Queen's beauty. They quickly fell in love and began to exercise joint rule in Alexandria. They also gave birth to a son and a daughter, leaving Octavian behind. Anthony actually became Caesar Lyon's stepfather. In order to consolidate their rule, Anthony and the Queen ordered the killing of their imprisoned former enemy, Queen Asinoa IV. However, Anthony stayed in Alexandria for not long before leaving Egypt and embarking on an eastern expedition to Parthia.

In 37 BC, Anthony returned from his expedition to the east. He reiterated his relationship with the queen, retired his wife Octavian, and emphasized that Alexandria was his home. Anthony and the queen formed a marriage according to Egyptian customs, but it was not recognized by the Romans. This also laid the groundwork for the rupture between Anthony and Octavian. After getting married, the two gave birth to another son. At the end of 34 BC, Antony returned from his eastern expedition to Armenia and announced that he would give all the territory of the Republic to the Queen and their children. The Queen and Caesar Lyon were respectively given the titles of "Queen of Kings" and "King of Kings", and became co rulers of Egypt and Syria; Antony and the Queen's three children were also divided into Armenia, Medes, Parthia, Cyrena, Libya, Phoenicia, and Cilicia, a move known as the "gift of Alexandria.". Furthermore, Antony declared Caesar Leon as Julius Caesar's biological son and legitimate heir, which was undoubtedly a huge provocation for Octavian, who claimed to be Caesar's adopted son and legitimate heir in Rome and ruled over the West of the Republic. The two officially broke off.
Anthony's actions angered the Romans, and Octavian took the opportunity to incite the Senate to declare war on Egypt. In the Battle of Aktium in 31 BC, the alliance of Antony and the Queen was defeated and retreated back to Alexandria.

Attempted escape and victimization
After the victory of the Battle of Aktium, Octavian led the Roman army to invade Egypt. The queen saw that the defeat was irreversible, so she sent the 17-year-old pharaoh Caesar Lyon to seek refuge in the port of Berniki by the Red Sea. It is said that there may be plans to flee to India and rebuild the Ptolemaic Kingdom. On August 1st, 30 BC, before the Roman army broke through the city, Antony committed suicide. On the same day, Octavian's army captured Alexandria, marking the annexation of Ptolemaic Egypt into the territory of the Roman Republic. On August 12th of the same year, the queen also committed suicide and passed away with Anthony. Caesar Lyon's servants, including his private tutor, mistakenly believed that Octavian's promise to send them back to Alexandria would forgive them, and sent the little pharaoh back to Alexandria, or rather they betrayed the little pharaoh (historical records are not accurate). Octavian was afraid that "too many Caesars" would threaten his position as the only heir to Caesar, so he ordered the execution of the pharaoh.
Octavian fully controlled Egypt and established it as a province of the Roman Republic (soon to become the Roman Empire), and proclaimed himself pharaoh. He claimed that his pharaoh title was inherited from his former pharaoh Caesar Lyon, whom he had killed. Although many monarchs, including Roman emperors who claimed to be pharaohs since Octavian, were only used in Egypt and not throughout the country, they were not recognized. The academic community generally regards 30 BC as the end of the pharaoh era.