How did Qin Shihuang get to be emporer of China?

The whole story is Qin Shi Huang (Ying Zheng)'s father Zi Chu was sent to Zhao Kingdom as hostage to assure the relationship between Qin and Zhao kingdom. Lü Buwei who was a rich merchant in Zhao with high rank in Zhao court played important role in this. He believe Zi Chu could help him make great achievement in fortune and political reputation. For Zi Chu's father (Ying Zheng's grandfather) didn't like Zi Chu and Zi Chu's mother, Lü Buwei spended a lot of money and persuaded another Madame Huayang whom Zi Chu's father liked best to adopt Zi Chu as her son, because Hua Yang didn't has a son. So, Zi Chu will be the future king of Qin. Lü Buwei gave a beauty (Zhao Ji) to Zi Chu to be his wife. Their son was Yi Zheng. He was born in Zhao and was named Zhao Zheng. Qin and Zhao's relationship went to bad later. Lü Buwei helped Zi Chu escaped from killed by Zhao and went back to Qin. Zhao Zheng and his mother covered by his grandmother so that they spent another few years in Zhao till Zi Chun get the crowne, Lü Buwei as his prime ministor. Zhao Zheng changed its name to Ying Zheng, Ying is the county's surname of Qin. Zi Chu died only three years after he became the king. Then 13-year-old Ying Zheng got to be the emperor, called himself Shi Huaung Di, meaning the first emperor.