The second grandson made a son
Lucius was the younger son of Agrippa and Julia the Elder, adopted by Augustus alongside his elder brother Gaius in 17 BCE. Like Gaius, he was advanced quickly through public honours and groomed for a future consulship and, implicitly, for a share in ruling after Augustus.
A sudden death in Gaul
In 2 CE, while travelling to Spain to take up a military assignment, Lucius fell ill and died suddenly at Massilia (modern Marseille). Tacitus reports later suspicion that Livia had a hand in the deaths of both Lucius and, two years afterward, Gaius, clearing the succession for her own son Tiberius — an allegation Tacitus himself presents as rumour rather than established fact. Lucius’s death, coming as it did before his brother’s, was the first blow to Augustus’s hopes of a direct bloodline succession.
Historical sources
Tacitus, Annals 1.3
The suspicion, reported but not endorsed, that Livia hastened the deaths of Gaius and Lucius.
Suetonius, Augustus 64–65
The adoption of Lucius and Gaius and Augustus’s grief at their deaths.
Portrait: Carole Raddato / Wikimedia Commons, CC BY-SA 2.0. Cropped and resized for display.