He was the great-grandson of Kim Seong-haeng (김성행), who was executed for supporting Prince Yeoning during the reign of King Gyeongjong.
[4] In 1824, at the age of 23, Kim Mun-geun passed the civil service examination (Heungje) held by King Sunjo at Huijungdang Hall, ranking 3rd out of all examinees.
In 1830, at the age of 29, he passed the civil service examination (Heungje) held by Crown Prince Hyomyeong at Chundangdae Hall.
In March of that year, he was appointed as the supervisor of the Seonggungam Gagyeok, a government office responsible for managing the royal ancestral shrines.
Following the accession of King Cheoljong, he was appointed as the Dongbu Seungji (Chief Secretary of the Eastern Bureau) in the Seungjeongwon (Royal Secretariat) in August 1851.
He was temporarily transferred to the position of Hanbuhogyun (Commander of the Royal Guards) before being promoted to Gukgu (National Relative) on the 24th of the eighth lunar month.
[5] In 1860, he faced criticism along with Kim Jwa-geun from the Count of Gyeongpyeong Yiho, the adopted son of Prince Punggye (King Cheoljong's paternal uncle) and his fifth cousin, according to the clan genealogy.
Yiho was exiled to Gangjin in Jeolla Province, stripped of his military title, and expelled from his adopted position as the son of Prince Punggye.
In December 1860, he was briefly appointed as the Governor of Gwangju-bu, but after just one month, he was reinstated as Yeongdonnyeongbusa (Minister of the Office of Royal Relatives).
Despite these criticisms, he was a skilled calligrapher and personally composed the epitaphs for his mother-in-law, Jeon Sangungbuin Lee, and his father-in-law, Jeongye Daewongun.
On November 7, after his death, he was posthumously promoted to the rank of Yeonguijeong (Chief State Councillor) and concurrently Yeonggyeongyeon Hongmungwan Chunchugwan Seonggyungwan Gwan sanggamsae (Chief of the Office of Censors) with the royal title of Daegwangboguksungrokdaebu (Great and Bright Protector of the Country, Highly Esteemed Great Father).