Incest of unequal gravity: the "incestus iuris gentium," which was applied to both Romans and non-Romans in the Empire, and the "incestus iuris civilis," which concerned only Roman citizens. Therefore, for example, an Egyptian could marry an aunt, but a Roman could not. Despite the act of incest being unacceptable within the Roman Empire, Roman Emperor Caligula is rumored to have had sexual relationships with all three of his sisters (Julia Livilla, Drusilla, and Agrippina the Younger). Emperor Claudius, after executing his previous wife, married his brother's daughter Agrippina the Younger, and changed the law to allow an otherwise illegal union.
Agrippina the Younger her younger sisters Julia Drusilla and Julia Livilla received various honours from their brother, which included but were not limited to: Around the time that Tiberius died, Agrippina had become pregnant. Domitius had acknowledged the paternity of the child. In the early morning hours in Antium of December 15, Agrippina gave birth to a son. Agrippina and Domitius named their son Lucius Domitius Ahenobarbus, after the Domitius' recently deceased father. This child would grow up to become the Emperor Nero. Nero was Agrippina's only natural child. Suetonius states that Domitius was congratulated by friends on the birth of his son,