Quick questions on The historical context for Qin Shi Huangdi: HSC Ancient History

Ying Zheng, the future First Emperor, was born in 259 BC not in Qin at all but at Handan, the capital of the rival state of Zhao. His father, the Qin prince Zichu (later King Zhuangxiang), was living there as a hostage, part of the era's practice of exchanging royal hostages to guarantee agreements between states. Zichu's fortunes, and so his son's, were tied to the wealthy merchant Lu Buwei, who financed and engineered the prince's return to Qin and his eventual accession to the throne. Later hostile tradition, recorded in the Shiji, even hinted that Lu Buwei, not Zichu, was Ying Zheng's true father, exactly the kind of scandalous claim a hostile successor tradition tends to preserve and that should be treated with caution.

By far the most important written source for Qin Shi Huangdi is the Shiji (Records of the Grand Historian), compiled by Sima Qian around 100 BC (completed roughly 94 to 91 BC). Its sixth chapter, the "Basic Annals of the First Emperor of Qin," is the backbone of almost everything we know about the reign, and Sima Qian drew on Qin records that had survived the dynasty's fall. He is an indispensable and often careful source.

What makes Qin Shi Huangdi so studiable is that, unlike many ancient figures, he can be checked against a wealth of contemporary archaeology unfiltered by Han hostility.