He was suffect consul for February through July of the year 18, succeeding the emperor Tiberius, and as the colleague first of Germanicus, then of Livineius Regulus.
[2] The consensus is that Tubero is one of the two brothers of Sejanus alluded to by Velleius Paterculus;[3] however, theories defining this fraternal relationship have changed over the years.
[4] Seius Tubero's first recorded action is in the year 16, as the commander of the cavalry under Germanicus in the battle against the Angrivarii.
[5] He next appears after his consulship, in the year 24, when he and Gnaeus Cornelius Lentulus Augur, described by Tacitus as leading men of the state and close friends of emperor Tiberius, were accused by Vibius Serenus of inciting rebellion and public unrest.
Because Lentulus was so old and Tubero in poor health, both were acquitted, and Serenus fled from Rome for Ravenna, only to be brought back before the Senate, tried, and punished with exile.