Jia Yi
Jia Dan was born in 730, during the reign of Emperor Xuanzong. His family was from Cang Prefecture (滄州, in modern Cangzhou, Hebei) and traced its ancestry to the Han Dynasty official Jia Yi, through officials of Cao Wei, Jin Dynasty (266–420), Liu Song, Southern Qi, Liang Dynasty, Northern Qi, Northern Zhou, Sui Dynasty, and Tang Dynasty. Both his grandfather Jia Zhiyi () and father Jia Yuanyan () served as county-level officials.