[note 1] The name Julio-Claudian is a historiographical term, deriving from the two families composing the imperial dynasty: the Julii Caesares and Claudii Nerones.

Adoption ultimately became a tool that most Julio-Claudian emperors utilized in order to promote their chosen heir to the front of the succession.

[3][4] Following Augustus' ascension as the first emperor of the Roman Empire in 27 BC, his family became a de facto royal house, known in historiography as the "Julio-Claudian dynasty".

Tiberius' connection to the Julian side of the Imperial family grew closer when he married Augustus' only daughter, Julia the Elder.

[5] 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.

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.

[citation needed] Lacking any male child and heir, Augustus married his only child—a daughter—Julia to his nephew Marcus Claudius Marcellus.

On Tiberius' request, Germanicus was granted proconsular power and assumed command in the prime military zone of Germania, where he suppressed the mutiny there and led the formerly restless legions on campaigns against Germanic tribes from AD 14 to 16.

Tiberius, perhaps sensitive to this ambition, rejected Sejanus's initial proposal to marry Livilla, Germanicus' sister and the widow of Tiberius' son Drusus the Younger, who had since died, in AD 25, but later had withdrawn his objections so that, in AD 30, Sejanus was betrothed to Julia Livia, daughter of Livilla and Drusus the Younger.

Suetonius writes that the Prefect of the Praetorian Guard Naevius Sutorius Macro smothered Tiberius with a pillow to hasten Caligula's accession.

[citation needed] Following Gemellus' death, Caligula marked his brother-in-law, Marcus Aemilius Lepidus, husband of his sister Julia Drusilla, as his heir.

On 24 January AD 41, the Praetorian tribune Cassius Chaerea and his men stopped Caligula alone in an underground passage leading to a theater.

[11] Despite his lack of political experience, and the disapproval of the people of Rome, Claudius proved to be an able administrator and a great builder of public works.

He took a personal interest in the law, presided at public trials, and issued up to twenty edicts a day; however, he was seen as vulnerable throughout his rule, particularly by the nobility.

He married four times (to, in order, Plautia Urgulanilla, Aelia Paetina, Valeria Messalina and, finally, Agrippina the Younger) and is referenced by Suetonius as being easily manipulated.

Messalina saw several members of the dynasty eliminated, notably arranging for the executions of Claudius' nieces Julia Livilla, daughter of Germanicus and Agrippina the Elder, and Julia Livia, daughter of Livilla and Drusus the Younger, as well as Julia Livilla's husband Marcus Vinicius, her mother's husband Appius Junius Silanus, Gaius Asinius Pollio, son of Tiberius' first wife Vipsania by her second husband and whose brother Servius Asinius Celer was also killed around this time, Claudius' son-in-law Gnaeus Pompeius Magnus, and his parents Marcus Licinius Crassus Frugi and Scribonia.

A number of ancient historians accuse Agrippina of poisoning Claudius, but details on these private events vary widely.

Like his maternal uncle Caligula before him, Nero was also a direct descendant of Augustus, a fact which made his ascension to the throne much easier and smoother than it had been for Tiberius or Claudius.

Ancient historians describe Nero's early reign as being strongly influenced by his mother Agrippina the Younger, his tutor Seneca, and the Praetorian Prefect Burrus, especially in the first year.

Other relatives whom Nero was believed to have had killed were Claudius' daughter by Aelia Paetina, Claudia Antonia, her husband and half-brother of Messalina, Faustus Cornelius Sulla Felix, Decimus Junius Silanus Torquatus, brother of Marcus and Lucius Junius Silanus Torquantus, as well as Marcus' son, also named Lucius, his aunt Domitia Lepida the Elder, and Rubellius Plautus, son of Julia Livia along with his wife, children and father-in-law.

By AD 65, senators complained that they had no power left and this led to the Pisonian conspiracy, led by Gaius Calpurnius Piso, an adoptive descendant of Triumvir Marcus Licinius Crassus, grandson of Gnaeus Calpurnius Piso, a governor of Syria who committed suicide after being accused of killing Germanicus, and first husband of Livia Orestilla, Caligula's second wife.

Vacancies after the conspiracy allowed Nymphidius Sabinus, a grandson of former imperial freedman Gaius Julius Callistus, who claimed to be an illegitimate son of Caligula, to rise in the Praetorian Guard.

In late AD 67 or early 68, Vindex, the governor of Gallia Lugdunensis in Gaul, rebelled against Nero's tax policies.

The Senate had been trying to preserve the dynastic bloodline by saving Nero's life, and were additionally reluctant to let someone who was not of the family become emperor; however, once he had committed suicide, and with Galba marching on the city, it had no choice but to declare him a public enemy posthumously.

Augustus' bloodline outlived his dynasty through the descendants of his first granddaughter, Julia the Younger, who married Lucius Aemilius Paullus and gave birth to Aemilia Lepida.

Her younger sister, Junia Lepida, married Gaius Cassius Longinus[16] and produced a daughter called Cassia Longina.

The Roman general Gnaeus Domitius Corbulo married Cassia, who provided him with two daughters, including Domitia Longina, later wife of the emperor Domitian.

Around AD 80 Lepidus had a daughter named Cassia Lepida, who married Gaius Julius Alexander Berenicianus, a descendant of Herod the Great, Ptolemy VI Philometor and Antiochus VIII Gryphus.

Apart from a son, Rubellius Plautus, executed by Nero in AD 62, Julia had a daughter or step-daughter, Rubellia Bassa, who married a maternal uncle of the future Roman Emperor Nerva by the name of Gaius Octavius Laenas.

[citation needed] The fact that ordinary father-son (or grandfather-grandson) succession did not occur has contributed to the image of the Julio-Claudian court presented in Robert Graves's I, Claudius as a dangerous world where scheming family members were all too ready to murder the direct heirs so as to bring themselves, their own immediate families, or their lovers closer to the succession.