Li Daozong
It is not known when Wei Daijia was born, but it was known that his family was from Yong Prefecture (雍州, roughly modern Xi'an, Shaanxi), the capital prefecture for both Tang Dynasty and its predecessor dynasty Sui Dynasty. Wei Daijia's grandfather Wei Chong () served as a minister during Sui, and his father Wei Ting () served as an official in late Sui and during Tang, under its first two emperors Emperor Gaozu and Emperor Taizong. Wei Daijia himself started his government career service as an officer in the imperial guard corps, and he married a daughter of the renowned general Li Daozong the Prince of Jiangxia (Emperor Taizong's cousin).