Emperor Xuanzong of Tang
Li Zhengji was born Li Huaiyu in 733, during the reign of Emperor Xuanzong of Tang. He was born in Tang's Pinglu Circuit (平盧, then headquartered in modern Chaoyang, Liaoning). As of 758, he served in the military at Pinglu Circuit's capital prefecture, Ying Prefecture (), along with his cousin Hou Xiyi ().