Yi Haeng was the first son and second child of Yi Geum, Prince Yeoning (later King Yeongjo), by one of his concubines, Lady Yi of the Hamyang Yi clan (함양 이씨; 咸陽 李氏), a former court lady.[1] He was born during the reign of his grandfather King Sukjong, but his birth was not made public, because his biological grandmother, Royal Noble Consort Suk, had died the previous year.
In 1720, King Sukjong was succeeded by his eldest son, Crown Prince Yi Yun (King Gyeongjong). As the new King was childless, his half-brother, Prince Yeoning, was appointed as Crown Prince (왕세제; 王世弟).
Hyojang's biological mother, Lady Yi, died the following year.
In 1724, after the death of King Gyeongjong, Yeoning was crowned as King Yeongjo, the 21st Joseon monarch. Yi Haeng was then given the title Prince Gyeongui (경의군; 敬義君) and in 1725, he was appointed as Crown Prince.
In 1726, Yeongjo selected Lady Jo of the Pungyang Jo clan, the only daughter of Jo Mun-myeong and a niece of Jo Hyeon-myeong, as his son's wife.
In 1728, the Crown Prince died in the palace Changgyeonggung, at the age of 9, after being ill for some months. The cause of his illness is unknown.[1] His death was devastating to King Yeongjo, who later gave Yi Haeng the posthumous nameHyojang.
His wife, who was later honored as Queen Hyosun, outlived by more than two decades. They are buried together, in the Samneung Cluster, in Paju, Gyeonggi Province. Their tombs are known as Yeongneung.[2]
After death
In 1735, seven years after his death, his half-brother Yi Seon (later known as Crown Prince Sado) was born and succeeded Hyojang as Crown Prince. In 1762, Sado was imprisoned in a wooden rice chest at the order of his father, King Yeongjo, and died 8 days later, leaving his son, Yi San, as the only royal male heir. Yeongjo was concerned that Yi San, being Sado's child, would be branded as "the son of a sinner" and thus become ineligible to succeed the throne, so in February 1764, he decreed that Yi San would become the adoptive son of the long-dead Crown Prince Hyojang.[3]
In 1776, King Yeongjo died of dementia and Yi San succeeded him as King Jeongjo. Surprisingly, on his coronation day, he announced to his courtiers, "I am the son of Crown Prince Sado".[4] In spite of this, Jeongjo respected the wishes of his grandfather and honored his adoptive father as King, and granted him the temple nameJinjong (진종; 眞宗). Hyojang's wife, the late Crown Princess Hyosun, was also honored as Queen.
In 1907, Hyojang was elevated to Emperor So (소황제; 昭皇帝) by Sunjong of Korea.
# denotes that the king was deposed and never received a temple name.
^Those who were listed were not reigning monarchs but posthumously recognized; the year following means the year of recognition.
^Only the crown princes that did not become the king were listed; the former year indicates when one officially became the heir and the latter one is that when one died/deposed. Those who ascended to the throne were excluded in the list for simplification.
^The title given to the biological father, who never reigned, of the kings who were adopted as the heir to a precedent king.
^The de jure monarch of Korea during the era was the Emperor of Japan, while the former Korean emperors were given nobility title "King Yi" instead.
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