He Was Adopted Into The Imperial Family

Marcus was born under the rule of Hadrian to the praetor Marcus Annius Verus, the emperor's nephew, and the heiress Domitia Calvilla. His mother and grandfather raised him when his father passed away when he was three. Hadrian chose Antoninus Pius, Marcus's uncle, as his new heir when his adopted son Aelius Caesar passed away in 138. Marcus and Lucius, the son of Aelius, were later adopted by Antoninus. That year, Antoninus succeeded Hadrian as emperor. Marcus, who was now the heir apparent, was taught Greek and Latin by teachers including Herodes Atticus and Marcus Cornelius Fronto. In 145, he wed Faustina, the daughter of Antoninus.

Marcus succeeded to the throne alongside his adopted brother Lucius Verus after Antoninus passed away in 161. Marcus, the imperial heir, was taught crucial principles like self-control and civic morality, which he would later come to exemplify. After Antoninus's lengthy and successful reign, Marcus was crowned emperor at the age of 40.