Sextus Pompeius was the youngest son of Pompey the Great (Gnaeus Pompeius Magnus) by his third wife, Mucia Tertia. His older brother was Gnaeus Pompeius, from the same mother. Both boys grew up in the shadow of their father, one of Rome's best generals and originally non-conservative politician who drifted to the more traditional faction when Julius Caesar became a threat.
When Caesar crossed the Rubicon in 49 BC, thus starting a civil war, his older brother followed their father in his escape to the East, as did most of the conservative senators. Sextus stayed in Rome in the care of his stepmother, Cornelia Metella. Pompey's army lost the battle of Pharsalus in 48 BC and Pompey himself had to run for his life. Cornelia and Sextus met him in the island of Mytilene and together they fled to Egypt. On the arrival, Sextus watched his father being killed by treachery on September 29 of the same year. After the murder, Cornelia returned to Rome, but in the following years Sextus joined the resistance against Caesar in the African provinces. Together with Metellus Scipio, Cato the younger, his brother Gnaeus and other senators, they prepared to oppose Caesar and his army to the end.
Caesar won the first battle at Thapsus in 46 BC against Metellus Scipio and Cato, who committed suicide. In 45 BC, Caesar managed to defeat the Pompeius brothers in the battle of Munda. Gnaeus Pompeius was executed, but young Sextus escaped once more, this time to Sicily.
Back in Rome, Julius Caesar was murdered on the Ides of March (March 15) 44 BC by a group of senators led by Cassius and Brutus. This incident did not lead to a return to normality, but provoked yet another civil war between Caesar's political heirs and his assassins. The second triumvirate was formed by Octavianus, Mark Antony and Lepidus, with the intention of avenging Caesar and subduing all opposition. Sextus Pompeius in Sicily was certainly a rebellious man, but the Cassius and Brutus faction was the second triumvirate's first priority. Thus, with the whole island as his base, Sextus had the time and resources to develop an army and, even more importantly, a strong navy operated by Sicilian marines.
Brutus and Cassius lost the twin battles of Philippi and committed suicide in 42 BC. After this, the triumvirs turned their attentions to Sicily and Sextus.
But by this time, Sextus was prepared for strong resistance. In the following years, military confrontations failed to return a conclusive victory for either side and in 39 BC, Sextus and the triumvirs sign for peace in the Pact of Misenum. The reason for this peace treaty was the incoming campaign against the Parthian Empire. Antony, the leader, needed all the legions he could get so it was useful to secure an armistice in the Sicilian front. The peace did not last for long. Octavianus and Antony's frequent quarrels were a strong political motivation for resuming the war against Sextus. Octavianus tried again to conquer Sicily, but he was defeated in the naval battle of Messina (37 BC) and again in August 36 BC. But by then, Octavianus had Marcus Vipsanius Agrippa, a very talented general, on his side. Only a month afterwards, Agrippa destroyed Sextus' navy in the shores of Naucholus. Sextus escaped to the East and, by abandoning Sicily, lost all his base of support.
Sextus Pompeius was caught in Miletus in 36 BC and executed without trial (a illegal act since Sextus was a Roman citizen) by orders of Marcus Titius, Antony's minion. His violent death would be one of the weapons used by Octavian against Antony several years later, when the situation between the two became unbearable.