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 Agrippina the Elder merely standing on a bridge waving the soldiers passing by, whereas her daughter eclipses her by presiding over a military tribunal and accepting gifts from foreign ambassadors. Tacitus also records serious tension between Agrippina and Livia. He describes Livia as having visited "stepmotherly provocations" on Agrippina. He says of Agrippina: "were it not that through her moral integrity and love for her husband she converted an otherwise ungovernable temper to the good" (Tacitus, "Annals" 1.33). Despite being sympathetic to her as a victim of imperial oppression, he uses expressions like "excitable", "arrogant", "proud", "fierce", "obstinate", and "ambitious"