 Since the accession of Tiberius, Drusus had been systematically groomed as the successor of his father, successfully commanding legions in Illyricum in 18, and sharing the consulship with Tiberius in 21. In practice it was still Sejanus who was the second man in the empire and he was ambitious to further expand his power. As early as 20, Sejanus had sought to solidify his connection with the imperial family, by betrothing his daughter Junilla to the son of Claudius, Claudius Drusus. At the time the girl was only 4 years old but the marriage was prevented, when the boy accidentally died a few days later of asphyxiation.
