From the King Chengtang (成汤), the throne of the Shang Dynasty passed on for 17 generations, with a total of 30 emperors, 14 of whom (9 generations) succeeded to the throne from their elder brothers. Although there was a difference between wife and concubine in the marriage form of the Yin royal family, it was not complete and perfect, and it failed to further determine which son of the legal wife should succeed to the throne. Therefore, the Shang Dynasty did not form a patriarch system that distinguished large and small patriarchal clans. The son succession system is the intermediary and bridge to the younger brother succession system. In the beginning, the heir to the throne is the son of the eldest brother, by the time of King Xiaoyi (小乙), the successor to the throne became the son of the youngest brother. After King Wuyi (武乙), the heir to the throne became the lineal eldest son. Although the kinship of the sons who succeeded to the throne changed constantly, it was basically the situation that the younger brother succeeded the older brother before King Wuyi, which showed the characteristics of the succession system of the Shang Dynasty. The Zhou Dynasty inherited the political legacy of the late Shang Dynasty, and established the strict lineal primogeniture system, which became one of the important political systems that remained unchanged for generations.