The mother of Yu Wen-hu wrote the following to him in a letter: "You and your brothers were born to me in Wu-ch'uan Town. The eldest has the sign of the rat, the second has the sign of the rabbit, and you have the sign of the snake."
周宗室宇文護的母親寫給他的信中就提到：「昔在武川鎮生汝兄弟，大者屬鼠；次者屬兔；汝身屬蛇。」