This is a study on three queens who were sisters in the Goryo dynasty. They were queen consorts of King Euijong, King Myongjong, and King Sinjong. Their father was Wang On, Duke Gangneung, who had been a member of the royal family.
In fact, Wang On's children could not maintain the membership unlike the father. In Goryo, the membership of the royal family was doomed to disconnect without a continuing marriage with royal members, such as kings, princes, and princesses. In Wang On's case, even though he himself had the membership, his wife did come from a noble family. Therefore, his children could not possess the membership of the royal household.
Wang On had six children. Five out of six offsprings repeated marriages with five children of King Injong. At first, Wang On's first daughter became a wife of the crown prince during the King Injong's reign. His two daughters and one son also married Injong's two princes and a princess during the reign of King Euijong. In addition, his fourth daughter became a wife of Injon's youngest son, too, during Myongjong's reign. Thus, two families have married five times. As a result, five children of Wang On could obtain the position as the members of the royal household.
In general, the crown succeeds to a crown prince. Thus, Wang On's first daughter became a queen[Empress Jangkyong] according to her husband, King Euijong. However, Military Revolt happened in 1170. Military leaders removed King Euijong, and placed his brother[King Myongjong] in a king's position. Later, a military leader, Choi, Chunghun, dethronded King Myongjong, and made his youngest brother[King Sinjong] as a new king. Because of those political disorders, King Euijong's two brothers became kings and their wives obtained the position of the queens[Empress Dowager Gwangjung and Empress Dowager Sunjung]. During the Military Rule, it seemed that the political position of queens was not that high. On the other hand, the queens were the relatives of the kings, and had children, and became mothers of crown princes. Therefore, the position as queens might have been relatively stable.