武承嗣
It is not known when Ji Xu was born, but it is known that he was from the Zhou capital Luoyang. He was said to be tall, good at hiding his emotions, but daring to speak. After passing the imperial examination, he was made the sheriff of Mingtang County (), one of the counties making up the western capital Chang'an. At that time, his father Ji Zhe () was serving as the prefect of Yi Prefecture (易州, in modern Baoding, Hebei) and was accused of receiving bribes, a capital offense. Ji Xu went to see Wu Zetian's powerful nephew Wu Chengsi and offered to have his two younger sisters become Wu Chengsi's servant girls. Ji Xu's sisters, after being delivered to Wu Chengsi's mansion, however, would not speak for three days, and he asked them why—and they responded, "Our father has violated the law and is set to be sentenced to death, and therefore we are worried." Wu Chengsi interceded on Ji Zhe's behalf, and Ji Zhe was spared.