Relations among the triumvirs were strained as the various members sought greater political power. Civil war between Antony and Octavian was averted in 40 BC, when Antony married Octavian's sister, Octavia. Despite this marriage, Antony carried on a love affair with Cleopatra, who bore him three children, further straining Antony's relations with Octavian. Lepidus was expelled from the association in 36 BC, and in 33 BC disagreements between Antony and Octavian caused a split between the remaining Triumvirs. Their ongoing hostility erupted into civil war in 31 BC, as the Roman Senate, at Octavian's direction, declared war on Cleopatra and proclaimed Antony a traitor. Later that year, Antony was defeated by Octavian's forces at the Battle of Actium. Antony and Cleopatra fled to Egypt, where they committed suicide.
With Antony dead, Octavian became the undisputed master of the Roman world. In 27 BC, Octavian was granted the title of Augustus, marking the final stage in the transformation of the Roman Republic into an empire, with himself as the first Roman emperor.
Antony's brother Lucius, on a coin issued at Ephesus during his consulship in 41 BC
According to the Roman orator Marcus Tullius Cicero, Antony's father was incompetent and corrupt, and was only given power because he was incapable of using or abusing it effectively. In 74 BC he was given military command to defeat the pirates of the Mediterranean, but he died in Crete in 71 BC without making any significant progress. The elder Antony's death left Antony and his brothers, Lucius and Gaius, in the care of their mother, Julia, who later married Publius Cornelius Lentulus Sura, an eminent member of the old Patrician nobility. Lentulus, despite exploiting his political success for financial gain, was constantly in debt due to the extravagance of his lifestyle. He was a major figure in the Second Catilinarian Conspiracy and was summarily executed on the orders of the Consul Cicero in 63 BC for his involvement. His death resulted in a feud between the Antonia and the famous orator.
Antony's early life was characterized by a lack of proper parental guidance. According to the historian Plutarch, he spent his teenage years wandering through Rome with his brothers and friends gambling, drinking, and becoming involved in scandalous love affairs. Antony's contemporary and enemy, Cicero, claimed he had a homosexual relationship with Gaius Scribonius Curio. There is little reliable information on his political activity as a young man, although it is known that he was an associate of Publius Clodius Pulcher and his street gang. He may also have been involved in the Lupercal cult as he was referred to as a priest of this order later in life. By age twenty, Antony had amassed an enormous debt. Hoping to escape his creditors, Antony fled to Greece in 58 BC, where he studied philosophy and rhetoric at Athens.