Antoninus was born at Rome, AD 121, on the 26th of April. His father, Annius Verus, died while he was praetor. His mother was Domitia Calvilla, also named Lucilla. The Emperor T. Antoninus Pius married Annia Galeria Faustina, the sister of Annius Verus, and was consequently the uncle of M. Antoninus. When Hadrian adopted Antoninus Pius and declared him his successor in the empire, Antoninus Pius adopted both L. Ceionius Commodus, the son of Aelius Caesar, and M. Antoninus, whose original name was M. Annius Verus. Antoninus then took the name of M. Aelius Aurelius Verus, to which was added the title of Caesar in AD 139: the name Aelius belonged to Hadrian's family, and Aurelius was the name of Antoninus Pius. When M. Antoninus became Augustus, he dropped the name of Verus and took the name of Antoninus. Accordingly he is generally named M. Aurelius Antoninus, or simply M. Antoninus.