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.
Henry V, Holy Roman Emperor Henry V, Holy Roman Emperor Henry V (; 11 August 1081/86 – 23 May 1125) was King of Germany (from 1099 to 1125) and Holy Roman Emperor (from 1111 to 1125), the fourth and last ruler of the Salian dynasty. Henry's reign coincided with the final phase of the great Investiture Controversy, which had pitted pope against emperor. By the settlement of the Concordat of Worms, he surrendered to the demands of the second generation of Gregorian reformers. Henry's parents were Henry IV, Holy Roman Emperor, and Bertha of Savoy. On 6 January 1099, his father had him crowned King