<P> Caligula (Gaius Julius Caesar Augustus Germanicus) was born into the Julian and Claudian branches of the Imperial family, thereby making him the first actual "Julio - Claudian" emperor . His father, Germanicus, was the son of Nero Claudius Drusus and Antonia Minor, the son of Livia and the daughter of Octavia Minor respectively . Germanicus was also a great - nephew of Augustus on his mother's side and nephew of Tiberius on his father's side . His wife, Agrippina the Elder, was a granddaughter of Augustus . Through Agrippina, Germanicus' children--including Caligula--were Augustus' great - grandchildren . When Augustus adopted Tiberius, the latter was required to adopt his brother's eldest son as well, thus allowing Germanicus' side of the Imperial family to inherit the Julius nomen . </P> <P> Claudius (Tiberius Claudius Caesar Augustus Germanicus), the younger brother of Germanicus, was a Claudian on the side of his father, Nero Claudius Drusus, younger brother of Tiberius . However, he was also related to the Julian branch of the Imperial family through his mother, Antonia Minor . As a son of Antonia, Claudius was a great - nephew of Augustus . Moreover, he was also Augustus' step - grandson due to the fact that his father was a stepson of Augustus . Unlike Tiberius and Germanicus, both of whom were born as Claudians and became adopted Julians, Claudius was not adopted into the Julian family . Upon becoming emperor, however, he added the Julian - affiliated cognomen Caesar to his full name . </P> <P> Nero (Nero Claudius Caesar Augustus Germanicus) was a great - great - grandson of Augustus and Livia through his mother, Agrippina the Younger . The younger Agrippina was a daughter of Germanicus and Agrippina the Elder, as well as Caligula's sister . Through his mother, Nero was related by blood to the Julian and Claudian branches of the Imperial family . However, he was born into the Domitii Ahenobarbi on his father's side . Nero became a Claudian in name as a result of Agrippina's marriage to her uncle, Claudius, who ultimately adopted her son as his own . He succeeded Claudius in AD 54, becoming the last direct descendant of Augustus to rule the Roman Empire . Within a year of Nero's suicide in AD 68, the Julio - Claudian dynasty was succeeded by the Flavian emperors following a brief civil war over the vacant Imperial throne . </P> <P> Lacking any male child and heir Augustus married his only daughter Julia to his nephew Marcus Claudius Marcellus . However, Marcellus died of food poisoning in 23 BC . Augustus then married his widowed daughter to his loyal friend, Marcus Vipsanius Agrippa, previously married to Augustus' niece, the sister of Marcellus . This marriage produced five children, three sons and two daughters: Gaius Caesar, Lucius Caesar, Julia the Younger, Agrippina the Elder, and Agrippa Postumus . </P>

Who was the last emperor of the augustinian line