The young Sejanus enjoyed the confidence of Augustus as his father had done. He succeeded him in command of the Prætorians, and was made adviser to Caius Cæsar when he went to the East. In this capacity he did his best to counteract the mischievous counsels of Marcus Lollius, and won the gratitude of Tiberius, which he soon improved into a personal friendship. As Sejanus was made his father’s colleague in B.C. 14, soon afterwards succeeding him in the sole command of the Prætorian guards, he cannot have been much younger than Tiberius, for he would hardly have been associated with his father before he was twenty years of age, and in that case Tiberius would have been his senior by only eight years. Even if we assume that Sejanus became his father’s colleague at the age of sixteen, an age at which young Romans commonly first entered on active service, he would still be only twelve years younger than Tiberius; but it is very improbable that so young a man would have been entrusted with the command of the Prætorians. The question is of some importance, for the language of the historians, perhaps unintentionally, conveys the impression that Sejanus was a comparatively youthful favourite of the Emperor’s, who owed his advancement to a blind partiality, whereas his acquaintance with Tiberius had been almost lifelong, even if we assume that he was little more than a boy when he first commanded the Prætorian guards. It is far more probable that there were only three or four years between the two men, and that the relations between Sejanus and Tiberius were comparable to those between Augustus and Agrippa. Paterculus, who admired Sejanus, is curiously apologetic about the obscurity of his family. He suggests that it was not so obscure as was generally supposed, and again that obscurity of descent is no bar to admission to the public service; he quotes very ancient examples, and the more modern ones of Marius, Cicero, and Asinius Pollio.