Zhou Dunyi
Hao was known as an outgoing, laid-back, and lively man, in contrast to his stern and severe younger brother. As Neo-Confucianism's popularity grew throughout the early second millennium AD, the two Cheng brothers along with Zhou Dunyi, Zhang Zai, Shao Yong, and Sima Guang became known as "The Six Masters of Northern Song" for their philosophical contributions.