Tacitus seems to think Sejanus was the manipulator of Tiberius and that Sejanus wanted the power for himself. But of course he has things in his way. Drusus, the adult son of Tiberius, who is about 37. And Drusus also had sons of his own. Tiberius Gemellus and his twin brother, Tiberius Germanicus II Gemellus, are about 4 years old. But of course the real heir to Augustus is Nero Julius Caesar – Germanicus’ eldest son. So something has to be done about them.