text: Birth and parentage According to the Records of the Grand Historian, written by Sima Qian during the Han dynasty, the first emperor was the eldest son of the Qin prince Yiren, who later became King Zhuangxiang of Qin. Prince Yiren at that time was residing at the court of Zhao, serving as a hostage to guarantee the armistice between the Qin and Zhao states. Prince Yiren had fallen in love at first sight with a concubine of Lü Buwei, a rich merchant from the State of Wey. Lü consented for her to be Yiren's wife, who then became known as Lady Zhao after the state of Zhao. He was given the name Zhao Zheng, the name Zheng () came from his month of birth Zhengyue, the first month of the Chinese lunar calendar; the clan name of Zhao came from his father's lineage and was unrelated to either his mother's name or the location of his birth. (Song Zhong says that his birthday, significantly, was on the first day of Zhengyue.) Lü Buwei's machinations later helped Yiren become King Zhuangxiang of Qin in 250 BC.
  However, the Records of the Grand Historian also claimed that the first emperor was not the actual son of Prince Yiren but that of Lü Buwei. According to this account, when Lü Buwei introduced the dancing girl to the prince, she was Lü Buwei's concubine and had already become pregnant by him, and the baby was born after an unusually long period of pregnancy. According to translations of the Annals of Lü Buwei, Zhao Ji gave birth to the future emperor in the city of Handan in 259 BC, the first month of the 48th year of King Zhaoxiang of Qin.