《新唐书·列传·卷一百一十》
家谱记载他的祖先是东周魏国的公子，秦灭了魏国后，到汉代迁到关中霸陵。因为他家原是王族，就姓王。
谱言其先本魏诸公子，秦灭魏，至汉徙关中霸陵，以其故王家，为王氏。
The genealogy records that his ancestors were the princes of the Wei kingdom of the Eastern Zhou Dynasty. After Qin destroyed Wei, they moved to Balin in Guanzhong during the Han Dynasty. Because his family was originally of royal lineage, they took the surname Wang.