, in Antium , near Rome. [9] [10] He was the only son of Gnaeus Domitius Ahenobarbus and Agrippina the Younger , sister of emperor Caligula . Lucius' father was grandson to Gnaeus Domitius Ahenobarbus and Aemilia Lepida through their son Lucius Domitius Ahenobarbus . Gnaeus was a grandson to Mark