the dugu sisters were part-xianbei, part-chinese sisters of the dugu clan who lived in the western wei (535–557), northern zhou (557–581) and sui (581–618) dynasties. all were daughters of the western wei general dugu xin. the eldest sister became a northern zhou empress, the seventh sister became a sui dynasty empress, and the fourth sister was posthumously honored as an empress during the tang dynasty (618–907). the seventh sister dugu qieluo, in particular, was one of the most influential women in ancient china history, owing to her closeness to her husband yang jian (emperor wen of sui) throughout their 45-year monogamous marriage.