Seonjo of Joseon
Early life

King Seonjo was born Yi Yeon in 1552 in Hanseong (today, Seoul), capital of Korea, as the third son of Prince Deokheung (덕흥군), himself son of King Jungjong and Royal Noble Consort Chang of the Ansan Ahn clan (창빈 안씨). On his mother's side, Yi Yeon was also a great-great-great-grandson of Princess Jeongui, the daughter of Queen Soheon and King Sejong. Princess Jeongui's granddaughter, Lady Ahn of the Juksan Ahn clan, married Jeong Sang-jo (정상조; 鄭尙祖), his great-grandfather and son of Jeong In-ji through his second wife, Lady Yi of the Gyeongju Yi clan. As well as Jeong Sang-jo being the younger half-brother of Jo Gwang-jo.

He was given the title of Prince Haseong, and was eventually adopted by Queen Insun. When King Myeongjong died young without an heir, Prince Haseong was the next in the line of succession. Then, by decision of the royal court, he was crowned king in 1567 at the age of 16. His father had the status of Grand Internal Prince (대원군, Daewongun, 'Great Prince of the Court).
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