Agrippa died in 12 BC, and Tiberius was ordered by Augustus to divorce his wife Vipsania Agrippina, daughter of Agrippa by his first marriage, and marry his stepsister, the twice-widowed Julia. Drusus, the brother of Tiberius, died in 9 BC after falling from a horse. Tiberius shared in Augustus' tribune powers, but shortly thereafter, in 6 BC, he went into voluntary exile in Rhodes. After the early deaths of both Lucius (AD 2) and Gaius (AD 4) and the exile of both Julia the Elder and Younger for adultery, a turn of events which saw the elder Julia's half brother Publius Cornelius Scipio exiled for treason, Mark Antony's son Iullus Antonius committing suicide and Julia the Younger's husband Lucius Aemilius Paullus being executed for conspiracy, Augustus was forced to recognize Tiberius as the next Roman emperor. Augustus banished his grandson Postumus Agrippa, who was adopted after the death of his brothers, to the small island of Planasia (around AD 6 or 7) where he was later executed, and Tiberius was recalled to Rome and officially adopted by Augustus. By Augustus' request, Tiberius adopted his nephew Germanicus, son of his late brother Drusus and biological great-nephew of Augustus through his mother. Germanicus subsequently married Augustus' granddaughter Agrippina.