Suetonius reports that Passienus was born at Visellium, an obscure town whose location has been lost. He was the grandson of Lucius Passienus Rufus, consul in 4 BC. His father, who died in AD 21, was a grandnephew of the historian Gaius Sallustius Crispus, who had no children of his own, and therefore adopted his sister's grandson as his heir. The elder Passienus assumed his uncle's names, in accordance with Roman custom, and in turn these names were passed to his son.
Early career
Passienus was a regular pleader in the court of the Centumviri, which met in the Basilica Julia. Suetonius mentions a statue of Passienus, which had been set up in the Basilica. He made his first speech in the senate during the reign of Tiberius, whom he addressed politely, and whose favour he won, although Suetonius maintains that the emperor's praise was insincere. Passienus was consul for the first time in AD 27, being named suffectus from the Kalends of July, as the colleague of Publius Cornelius Lentulus, and serving out the remainder of the year. Despite his rank and wealth, Passienus affected a humble manner in order to remain in favour with the emperors. During the reign of Caligula, he accompanied the emperor on his travels, following on foot as a token of subservience. Caligula is said to have asked him once, in private, if Passienus had ever had intercourse with his own sister, as he himself had done. Realizing that answering either in the affirmative or the negative might be dangerous, Passienus cleverly replied, "not yet", thereby avoiding the emperor's displeasure.
Passienus' wife, Domitia, was the sister of Gnaeus Domitius Ahenobarbus, and thus the sister-in-law of Agrippina. Domitia's first husband, Decimus Haterius Agrippa, consul in AD 22, had died in 32 after advocating the condemnation of Lucius Fulcinius Trio and Publius Memmius Regulus, the feuding consuls of the previous autumn, thus drawing the public ire on himself. Passienus married Domitia the following year, and became the stepfather of Quintus Haterius Antoninus, who would become consul under Claudius in AD 53. Shortly after his accession in 41, the emperor Claudius asked Passienus to divorce his wife, and marry Agrippina, for her husband Domitius Ahenobarbus had recently died. Agrippina was a sister of Caligula, and had married a man with a reputation for needless cruelty, who had nearly been put to death by Tiberius, and been saved only by the emperor's death. She herself had been exiled by Caligula in AD 39, due to her supposed involvement in a plot against the emperor, with her brother-in-law and alleged paramour, Marcus Aemilius Lepidus. After her husband's death, Caligula had seized the inheritance that rightfully belonged Agrippina's young son, Lucius. Caligula was assassinated shortly thereafter, and his uncle, Claudius, eager to restore the appearance of respectability to the imperial family, recalled Agrippina from exile, restored her son's inheritance, and hoped to provide her with a worthy husband. Domitia was also the emperor's cousin, but it was more important to rehabilitate Agrippina's image, so Passienus acquiesced to Claudius' wishes, divorcing Domitia and becoming the husband of Agrippina, as well as the stepfather of the future emperor Nero.
Downfall and legacy
For the term June 42 through June 43, the sortition selected Passienus proconsular governor of Asia. Ronald Syme once described this office as "of the highest dignity in the senatorial career." Then in 44, Passienus was consul for the second time, but this time as consul ordinary, with Titus Statilius Taurus as his colleague. His second consulship was a special honour, but partly symbolic, as he was expected to resign before the expiration of six months, and probably did so on the Ides of January. He was followed by Publius Pomponius Secundus, who held the fasces with Statilius until the Kalends of July. By now, Passienus was the most prosperous of men: twice consul, the grandson of a consul, the heir of Sallust, he had twice married into the imperial family. His fortune was valued at two hundred million sestertii. He was persuaded by Agrippina to name her as his heir; this proved to be his undoing, for he died by his wife's treachery, probably poisoned, about AD 47. This would not be the end of Agrippina's villainy, for Claudius' wife, Messalina, correctly perceiving the threat from Agrippina, attempted to have Lucius assassinated, in order to ensure the succession of Britannicus, her own son by the emperor. The attempt failed, and, after procuring Passienus' death, Agrippina worked to bring about the downfall of Messalina. She then seduced her uncle, the emperor, becoming his wife, and persuaded Claudius to adopt Lucius, naming him his heir in preference to his own son. Agrippina then procured the emperor's death, placing her son, now the emperor Nero, on the throne; he soon disposed of Britannicus. Agrippina met her end in 59, when Nero had her murdered. Her predecessor, Domitia, died later that year, and there was a rumour that Nero had poisoned her as well. Gaius Passienus Crispus was an intelligent, humble, and witty person, famous for his epigram to the effect "that the world never knew a better slave, nor a worse master", referring to the future emperor Gaius and his grandfather, Tiberius.
