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.
Emperor Xiaojing of Eastern Wei do her husband harm, kept close watch on her husband, often tasting his food to make sure that it was not poisoned. However, Emperor Wenxuan was apprehensive of the former emperor. Around the new year 552, Emperor Wenxuan invited the Princess Taiyuan to a feast inside the palace. As soon as she left her residence, Emperor Wenxuan sent assassins to force the former emperor to drink poisoned wine, and also killed his three sons. Emperor Wenxuan gave the former emperor the posthumous name of Xiaojing, and also buried him with imperial honors. However, at a later time, for reasons unknown,