Historically, the emperor skipped his son and passed the throne directly to his grandson, and it was generally the crown prince who died before the emperor. Here are a few examples:
1. Yelu Hongji of Liao Daozong passed the throne to the emperor's grandson Yelu Yanxi. Before passing the throne to Yelu Yanxi, the crown prince Yelu Jun had been framed to death by traitors, and he was in guilt, and Yelu Hongjili, Yelu Yanxi, the son of Yelu Jun, was the emperor's grandson. Not long after Yelu Yanxi (Emperor Tianzuo) ascended the throne, he indulged in hunting and abandoned the government, and later Liao was destroyed by Jin.
Second, Jin Shizong completed Yan Yong's throne to the emperor's grandson Wan Yan Jing. When Jin Shizong was on his northern tour, the crown prince Wanyan Yungong died of illness, and he was entangled in his heart for a long time whether to pass on the throne to his son or grandson. In the end, he set up Yan Yungong's son Wan Yan Jing as the emperor's grandson. After Yan Jing ascended the throne, he implemented comprehensive sinicization, but in the later period, he favored traitorous ministers, the government was corrupt, and the Jin State began to decline.
3. Kublai Khan, the ancestor of the Yuan dynasty, passed on the throne to the emperor's grandson Timur. Before the succession, the crown prince Zhenjin died of illness, so Kublai Khan established the third son of Zhenjin Timur as the emperor's grandson, which was the future Yuan Chengzong.
Fourth, Zhu Yuanzhang, the Taizu of the Ming Dynasty, passed on the throne to Zhu Yunwen, the grandson of the emperor. Since the death of the crown prince Zhu Biao in April of the 25th year of Hongwu, Zhu Yuanzhang decided to appoint Zhu Biao's second son Zhu Yunwen as the emperor's grandson after several months of consideration. After Zhu Yunwen ascended the throne, he cut the feudal domain, and Zhu Di, the king of Yan, rebelled, and finally drove out Emperor Jianwen and became emperor himself.
The above are several examples of emperors skipping their sons and passing on their grandsons directly, and in general, they were not very successful.
