Roman civil law prohibited marriages within four degrees of consanguinityPatrick Colquhoun, A Summary of the Roman Civil Law, Illustrated by Commentaries on and Parallels from the Mosaic, Canon, Mohammedan, English, and Foreign Law (London: Wm. Benning & Co., 1849), p. 513-4 but had no degrees of affinity with regard to marriage. Roman civil laws prohibited any marriage between parents and children, either in the ascending or descending line ad infinitum. Adoption was considered the same as affinity in that an adoptive father could not marry an unemancipated daughter or granddaughter even if the adoption had been dissolved. Incestuous unions were discouraged and considered nefas (against the laws of gods and man) in ancient Rome. In AD 295, incest was explicitly forbidden by an imperial edict, which divided the concept of incestus into two categories 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. The law prohibiting marrying a sister's daughter remained. The taboo against incest in ancient Rome is demonstrated by the fact that politicians would use charges of incest (often false charges) as insults and means of political disenfranchisement.
Roman civil law prohibited marriages within four degrees of consanguinityPatrick Colquhoun, A Summary of the Roman Civil Law, Illustrated by Commentaries on and Parallels from the Mosaic, Canon, Mohammedan, English, and Foreign Law (London: Wm. Benning & Co., 1849), p 513-4 but had no degrees of affinity with regard to marriage. Roman civil laws prohibited any marriage between parents and children, either in the ascending or descending line ad infinitum. Adoption was considered the same as affinity in that an adoptive father could not marry an unemancipated daughter or granddaughter even if the .adoption had been dissolved. Incestuous unions were discouraged and considered nefas (against the laws of gods and man) in ancient Rome. In AD 295, incest was explicitly forbidden by an imperial edict, which divided the concept of incestus into two categories 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. The law prohibiting marrying a sister's daughter remained. The taboo against incest in ancient Rome is demonstrated by the fact that politicians would use charges of incest (often false charges) as insults and means of political disenfranchisement.