King Zhaoxiang of Qin
In 306 BC, the young King Zhaoxiang ascended to the throne, with his mother Queen Dowager Xuan serving as regent. Knowing Qin could not focus on eradicating Yiqu when it had the hostile eastern states to deal with, and her son's rule was still shaky due to numerous rival princes keen to capture the throne, Queen Dowager Xuan decided to use an approach of pretended conciliation. She invited the king of Yiqu to live long-term in the Ganquan Palace, and consummated a seductive liaison that produced two sons with him. This completely removed the Yiqu King's hostility towards Qin, as the beguiled king had lost all cautiousness around the Queen Dowager. At the same time, King Zhaoxiang was aggressively acting to weaken rival warring states in the east and south, and Queen Dowager Xuan was secretly planning with her son the eventual annihilation of Yiqu.
Yao Xing
When Yao Chang declared a rebellion and established Later Qin in 384, Yao Xing was at the Former Qin capital Chang'an, and he immediately fled to his father. For the next several years, as Yao Chang fought with Former Qin and Western Yan, Yao Xing was often entrusted with guarding the base of operations (initially Beidi (北地, in modern Tongchuan, Shaanxi), later Chang'an after Western Yan captured and then abandoned it), while his father engaged in campaigns. In 386, after Yao Chang declared himself emperor, he created Yao Xing crown prince. He was considered to be firm and gracious, and he spent much time studying literature despite the work necessary in maintaining home base. In 392, while Yao Chang was away on a campaign, Yao Xing, at the suggestion of the general Yao Fangcheng (姚方成), executed a number of Former Qin generals whom Yao Chang had taken captive earlier. While Yao Chang was angry on the surface, he appeared to be secretly happy that Yao Xing realized the danger that these generals posed. In 393, when the Former Qin emperor Fu Deng attacked the Later Qin vassal Dou Chong (竇衝), Yao Chang, at the suggestion of the prime minister Yin Wei (尹緯), sent Yao Xing against Fu Deng, in order to establish Yao Xing's authority over the troops. Yao Xing was able to stop Fu Deng's attack on Dou fairly easily.