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.
Yang Zhao was their oldest son. In his infancy, he was raised by his grandparents Emperor Wen and Empress Dugu. In 590, Emperor Wen created him the Prince of Henan. He initially married the daughter of the official Cui Hongsheng (崔弘昇) as his wife and princess, but after Princess Cui's aunt, who married his uncle Yang Jun the Prince of Qin, was discovered to have poisoned Yang Jun over her jealousness for Yang Jun's concubines in 597, Yang Zhao divorced his wife and married the daughter of the official Wei Shou (韋壽) the Duke of Hua as his wife and princess. After