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According to the Records of the Grand Historian, written by Sima Qian during the next dynasty and avowedly hostile to Qin Shi Huang, the first emperor was not the actual son of King Zhuangxiang of Qin.
By the time Lü Buwei introduced the dancing girl Zhào Jī ( 趙姬, or the Concubine from Zhao ) to the future King Zhuangxiang of Qin, she was allegedly Lü Buwei's concubine and had already become pregnant by him.
According to translations of the Annals of Lü Buwei the woman 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.
The idea that the emperor was an illegitimate child added to the negative view of him for most of the next 2000 years after his death.
Today there is skepticism amongst some scholars about this claim as recorded by Sima Qian.
There is some inconsistency between the date of birth and the theory of Lü Buwei being the real father of the first emperor.
In the view of some scholars, the length of the pregnancy, lasting a full year if the accusation is true, is impossible according to modern medicine.
Professors John Knoblock and Jeffrey Riegel, in their translation of Lü Buwei's Spring and Autumn Annals, call the story " patently false, meant both to libel Lü and to cast aspersions on the First Emperor.

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