Joseon founding merit subject honored as first-generation ancestor of the Gaeseong Yi clan; renamed Yi Gae (李開); posthumous title Munjeong
| Life | 미상 ~ 미상 |
| Era | 고려 말~조선 초 |
| Clan | 개성 이씨 |
Yi Deok-si (李德時) lived from late Goryeo into early Joseon and was a grandson of Yi Cha-gam, the founder of the Gaeseong Yi clan. He is said to have changed his name to Yi Gae (李開), and his descendants took him as first-generation ancestor and fixed Gaeseong as the ancestral seat. Wikipedia calls him the mid-founder.
In Goryeo he rose to tonghun daebu (some sources write tongjeong daebu) and, having helped Yi Seong-gye, was named a Joseon founding merit subject (gaeguk wonjong gongsin). Records say he was posthumously raised to jahon daebu and Minister of Taxation and given the title Munjeong-gong, though accounts of the posthumous office and title differ by source.
His son Yi Deung married Uiryeong, an illegitimate daughter of Yi Seong-gye, and became Gyecheon-wi; his grandson Yi Seon is said to have served as a minister.
The founder Yi Cha-gam is said to have served as nok-sa-ryeong and dongjeong under King Chungsuk of Goryeo, then as magistrate of Gaeseong, where he settled; he is said to have split off from the Cheongju Yi. His grandson Yi Deok-si, that is Yi Gae, was taken as first-generation ancestor with Gaeseong as the seat, and the clan's lineage continues from him.
He is said to have been named a founding merit subject (gaeguk wonjong gongsin) for his part in founding Joseon. The wonjong rank was a way of rewarding a broad group of deserving persons beyond the principal merit subjects. His specific deeds and life dates were not confirmed here.
The location of his grave was not confirmed here.
His son Yi Deung (Gyecheon-wi) and grandson Yi Seon (minister) are recorded; Yi Seon's son Yi Gwang-se is said to have served as a county magistrate under King Sejong.