Gaius Caesar was a grandson and heir to the throne of Roman emperor Augustus, alongside his younger brother Lucius Caesar. Although he was born to Marcus Vipsanius Agrippa and Julia, Augustus' only daughter, Gaius and Lucius were raised by their grandfather as his adopted sons and joint-heirs. He experienced an accelerated political career befitting a member of the Julio-Claudian dynasty, with the Roman Senate allowing him to advance his career without first holding a quaestorship or praetorship, offices that ordinary senators were required to hold as part of the cursus honorum.

Lucius Caesar was a grandson of Augustus, the first Roman emperor. The son of Marcus Vipsanius Agrippa and Julia the Elder, Augustus' only daughter, Lucius was adopted by his grandfather along with his older brother, Gaius Caesar. As the emperor's adopted sons and joint-heirs to the Roman Empire, Lucius and Gaius had promising political and military careers. However, Lucius died of a sudden illness on 20 August 2 AD, in Massilia, Gaul, while traveling to meet the Roman army in Hispania. His brother Gaius also died at a relatively young age on 21 February 4 AD. The untimely loss of both heirs compelled Augustus to redraw the line of succession by adopting Lucius' younger brother, Agrippa Postumus as well as his stepson, Tiberius on 26 June 4 AD.