When Emperor Wu ascended the throne in 265, he honored his mother Wang Yuanji as empress dowager. In 266, he also honored his aunt Yang Huiyu (Sima Shi's wife) an empress dowager, in recognition of his uncle's contributions to the establishment of the Jìn Dynasty. He made his wife Yang Yan empress the same year. In 267, he made her oldest living son, Sima Zhong crown prince—based on the Confucian principle that the oldest son by an emperor's wife should inherit the throne—a selection that would, however, eventually contribute greatly to political instability and the Jin Dynasty's decline, as Crown Prince Zhong appeared to be developmentally disabled and unable to learn the important skills necessary to govern. Emperor Wu further made perhaps a particularly fateful choice on Crown Prince Zhong's behalf—in 272, he selected Jia Nanfeng, the strong-willed daughter of the noble Jia Chong, to be Crown Prince Zhong's princess. Crown Princess Jia would, from that point on, have the crown prince under her own tight control. Before Empress Yang died in 274, she was concerned that whoever the new empress would be, she would have ambitions to replace the crown prince, and therefore Empress Yang asked Emperor Wu to marry her cousin Yang Zhi. He agreed.