One of the major themes later in Emperor Xuanzong's reign was the high-level officials' concerns that he was not creating a Crown Prince, as this refusal to do so left the imperial succession uncertain. The issue was raised repeatedly, including by chancellors Wei Mo, Pei Xiu (Tang dynasty), and Cui Shenyou, but he rebuffed all of them, leading to Pei's resignation and Cui's removal. (The reason why Emperor Xuanzong repeatedly refused to create a crown prince was said to be his disfavor for his oldest son Li Wen the Prince of Yun and favor for his third son Li Zi the Prince of Kui. He wanted Li Zi to be his heir, but was hesitant to create Li Zi crown prince because Li Zi was not the oldest.)
