King Zhaoxiang of Qin
Because King Zhaoxiang had not yet legally come of age (traditionally at the age of 20), his mother, who was now known as Queen Dowager Xuan, became the regent. She was supported by her brothers, Wei Ran and Mi Rong (羋戎), as well as two other sons, Prince Yi (公子悝) and Prince Fu (公子巿), the four of them collectively known as the "Four Nobles" (四貴).
Duke Kang of Qin
Duke Kang was one of the 40 sons of his father Duke Mu of Qin, and succeeded Duke Mu as ruler of Qin when he died in 621 BC. In the same year Duke Xiang of Jin also died, starting a succession crisis in Qin's neighbouring state Jin. Zhao Dun, the powerful minister of Jin, initially wanted to install Duke Xiang's younger brother Prince Yong on the Jin throne. Prince Yong was at the time exiled in Qin, and in 620 BC Qin sent an army to escort Yong back to Jin. However, Zhao Dun soon changed his mind and instead made Duke Xiang's young son Yigao the ruler, later known as Duke Ling of Jin. Jin then dispatched an army to stop Prince Yong, and defeated the Qin escort force at Linghu.