Emperor Suzong of Tang , personal name Li Heng, n Li Sisheng , known as Li Jun from 725 to 736, known as Li Yu from 736 to 738, known briefly as Li Shao in 738, was an emperor of the Tang Dynasty and the son of Emperor Xuanzong. Suzong ascended the throne after his father fled to Sichuan during the An Shi Rebellion in 756 Li Heng himself had fled in the opposite direction, to Lingwu, where he was declared emperor by the army. Much of Emperor Suzongs reign was spent in quelling the aforementioned rebellion, which was ultimately put down in 763 during the reign of his son Emperor Daizong.
Li Sisheng was born in 711, during the second reign of his grandfather Emperor Ruizong, as the third son of his father, then the Crown Prince, Li Longji, who would later become Emperor Xuanzong. His mother Consort Yang Guipin was from the imperial clan of the preceding Sui Dynasty. Her greatgrandfather Yang Shida was a high level official during Sui and had been given the title Prince of Zheng . Her father Yang Zhiqing was a general of the imperial guards during Tang. At the time that Consort Yang Guipin was pregnant with Li Sisheng, Li Longji was locked in a power struggle with his aunt, Emperor Ruizongs sister Princess Taiping, and it was said that Princess Taiping had placed many associates in the crown princes palace to spy on Li Longji and that she did not want him to have many sons. and Li Siqian, later named Li Ying . Li Longji was worried that, if Princess Taiping found out that Yang Guipin was pregnant, Princess Taipings associates might harm him, and he spoke to a close a
Source: Wikipedia