Iullus Antonius also. Through his half-sister Antonia Minor, he was a maternal uncle of Germanicus, Livilla and the Emperor Claudius. Lastly, he was a paternal great-uncle of the Emperor Caligula, Julia's grandson by Agrippa, and the Empress Agrippina the Younger, Julia's eldest granddaughter, and Claudius' niece and fourth wife, as well as other children fathered by Germanicus and his wife Agrippina the Elder: Nero Julius Caesar, Drusus Caesar, Julia Drusilla, and Julia Livilla. Through Agrippina the Younger, Iullus was a maternal great-great-uncle of the Emperor Nero. Through his half-sister Antonia Major and stepsister Claudia Marcella Minor, he was also great-uncle to Claudius'
Agrippina the Elder was made "princeps". While Germanicus was administering the oath of fealty to Tiberius, a mutiny began among the forces on the Rhine. During the mutiny, Agrippina brought out their sixth child, Gaius, and made preparations to take him away to a safer town nearby. He was in a full army outfit including the legionary hobnailed boots ("caligae"). These military-booties earned Gaius the nickname "Caligula" (lit. "little boots"), and garnered sympathy for Agrippina and the child among the soldiery. Tacitus attributes her actions as having quelled the mutiny (Tacitus, "Annals" 1.40–4). Once the mutiny was put to an end, Germanicus allowed