Collatinus was the son of Arruns Tarquinius, better known as Egerius, a nephew of Lucius Tarquinius Priscus, the fifth King of Rome. Through an accident, Arruns had been born into poverty, but when his uncle subdued the Latin town of Collatia, he was placed in command of the Roman garrison there. The surname Collatinus was derived from this town. Collatinus married Lucretia, daughter of Spurius Lucretius Tricipitinus. According to legend, while Collatinus was away from home, his cousin, Sextus Tarquinius, son of the king, Lucius Tarquinius Superbus, came to his house by night. Forcing himself upon Lucretia, Sextus threatened to kill her, together with a slave, and tell her husband that he had caught her in the act of adultery with the slave, unless she should accede to his desire. After his departure, Lucretia sent for her husband and father, and recounted the events to them. Despite their entreaties and protests of her innocence, Lucretia then plunged a dagger into her breast in expiation of her shame.
Revolution
Enraged by his cousin's deed, Collatinus and his father-in-law brought news of the crime before the people. They were supported by Brutus, the king's nephew, and others who had suffered various cruelties at the hands of the king and his sons. While the king was away on a campaign, the conspirators barred the gates of Rome and established a republican government, headed by two consuls, so that one man should not be master of Rome. Brutus and Collatinus were the first consuls, and set about the defense of the city. Collatinus' ascendency was short-lived; although he himself had suffered at the hands of the king, and ushered in the Republic, he soon became the object of revulsion from those who would not abide any of the Tarquins in power at Rome. Collatinus was dumbstruck when Brutus, his colleague and cousin, called upon him to resign, but resisted until his father-in-law, Lucretius, added his voice to the chorus. Fearing what might become of him should he refuse the popular demand, Collatinus laid down the consulship and went into exile at Lanuvium. Brutus, who as the king's nephew was even closer to the royal house, was spared the same indignity, as a part of the Junia gens; but he fell in battle the same year against the king's forces. Publius Valerius Poplicola was appointed consulsuffectus in the place of Collatinus, and the elderlySpurius Lucretius in place of Brutus; but he died soon after, and Marcus Horatius Pulvillus became consul in his place, the fifth and final consul of the first year of the Republic.
