Lady Gang (Queen Shindeok 神德王后, ?~1396)
Yi Seong-Gye had two wives. One is Lady Han (Queen Shinui of the Anbyeon Han clan) and the other is Lady Gang (Queen Sindeok of the Goksan Kang clan). While Bang-Won’s mother, Lady Han, was living in Hamju, General Yi’s house in the capital was in charge of Lady Gang who belongs to prestigious noble clan.
It was a unique dual marriage system for high-class Goryeo nobles. If a country nobleman gets a high government post and goes up to the capital, he left his wife in his hometown, and married a daughter of a powerful clan in the capital. Both of them were equally his legitimate wives, but in most cases, a capital wife (경처, 京妻) had stronger power than a hometown wife (향처, 鄕妻) due to their social status.
Yi Bang-Won’s mother Lady Han was General Yi’s hometown wife and had kept alive in Hamju until 1391. She died shortly before the establishment of Joseon. I guess the scriptwriters intentionally skewed the historical fact in ep 19 because they didn’t cast her.
Lady Gang was General Yi’s capital wife. That’s why Bang-Won and his wife called her “Gagyeong mother” in ep 19. She was supposed to be 20 years younger than Yi Seong-Gye. She was the biggest supporter of her husband. She gave birth to two sons : Yi Bang-Beon (7th) and Yi Bang-Seok (8th). General Yi loved her so much that it became a serious cause of trouble in the future.