Why are Xiao Bai and Zhu Yilong both Aries, but their personalities are totally different?

White and Zhu Yilong, when compared together, have different personalities, which is actually due to the influence of stereotypes brought by astrology. Usually, the Aries boys in people's eyes should be enthusiastic, brave, naive and expressive, while White fits this description very well and is a typical Aries boy, but Zhu Yilong doesn't seem to fit this description. He is gentle, calm and introverted.