Cui Yan
It is not known when Cui Zhaowei was born. His biographies in the "Old Book of Tang" and the "New Book of Tang" both indicated that he was from the prominent Cui clan of Qinghe, which was descended from the Spring and Autumn period state Qi; and the table of the chancellors' family trees in the "New Book of Tang" further traced him specifically to the "Southern Ancestor" branch of the clan, which included officials of Han Dynasty, Cao Wei, Jin Dynasty (266–420), Later Zhao, Liu Song, Northern Wei, Northern Qi, Northern Zhou, and Tang Dynasty. According to Cui Zhaowei's biography in the "Old Book of Tang", his grandfather Cui Bi (崔庇) served as a county sheriff, while his father Cui Yan (崔巘) served as the governor of Eyue Circuit (鄂岳, headquartered in modern Wuhan, Hubei), but the table of the chancellors' family trees in the "New Book of Tang" do not describe Cui Bi and Cui Yan as having those offices, and Cui Zhaowei's biography in the "New Book of Tang" omitted references to them altogether. Cui Zhaowei had at least two older brothers, Cui Zhaofu (崔昭符) and Cui Zhaoyuan (崔昭原), and at least one younger brother, Cui Zhaoju (崔昭矩).