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 Elder to Augustus, a significant factor in the marriages of the emperors and princes of the dynasty. The Annals repeatedly has Agrippina competing for influence with Tacitus simply because she is related to Augustus biologically. Tacitus presents Agrippina as being kindred to aristocratic males, and has her reversing gender roles, which showcases her assumption of male "auctoritas" ("authority") with metaphors of her dressing and undressing. In an example of Agrippina assuming "auctoritas", he says: Using the above epithet, ""(femina) ingens animi"" ("..[a woman], great for her courage"), he assigns a haughty attitude to Agrippina that compels her to explore the affairs