Born after his father’s death
Agrippa Postumus was the youngest son of Agrippa and Julia the Elder, born after his father’s death in 12 BCE — hence the name Postumus. After the deaths of his elder brothers Gaius and Lucius, Augustus adopted him alongside Tiberius in 4 CE, briefly making him, on paper, one of two potential heirs.
Disgrace and exile
Ancient sources describe Postumus as coarse and violently tempered, though how much of this reflects genuine unsuitability versus a convenient justification for sidelining him is debated. In 7 CE Augustus disowned him and had him exiled to the island of Planasia, removing him from any realistic path to power.
Killed at the moment of succession
Postumus was killed by a centurion immediately after Augustus’s death in 14 CE, before Tiberius’s accession was even public knowledge. Ancient authors disagree about who gave the order — Augustus before his death, or Livia and Tiberius after it — but the effect was the same: the last rival with a plausible blood claim to Augustus’s position was removed at the exact moment Tiberius needed the succession secured. See how Tiberius became emperor for the fuller, sourced account.
Historical sources
Tacitus, Annals 1.6
The killing of Agrippa Postumus and the uncertainty over who ordered it.
Suetonius, Augustus 65
Postumus’s disgrace, character, and exile.
Portrait: José Luiz Bernardes Ribeiro / Wikimedia Commons, CC BY-SA 4.0. Resized for display.