Korean Clans (Bon-gwan): Why So Many Kims, How to Tell Which Kim Clan, and What to Say When Asked

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Last updated: 30 October 2026 (census figures re-read from the Statistics Korea 2015 complete-enumeration release, the latest published surname count; clan origins from the Academy of Korean Studies' Encyclopedia of Korean Culture; marriage law from the Constitutional Court and the encyclopedia's entry on the old same-clan marriage ban)

Short answer: what is a Korean clan, and why are there so many Kims? A Korean clan is a surname plus a bon-gwan (본관, 本貫), the ancestral seat the line is named after. "Kim" is only half of a person's clan identity. Gimhae Kim (김해 김씨) and Gyeongju Kim (경주 김씨) write the same surname, 金, but they are separate clans with separate founders: King Suro of Gaya for one, Kim Alji of Silla for the other. Kim is common because the name belonged to two royal houses, because people who took surnames late tended to copy the big, prestigious clans, and because a 1909 registration law gave everyone a surname and a bon. Statistics Korea's 2015 census counted 10.69 million Kims, 21.5% of Korean nationals, roughly one in five. Gimhae Kim alone was 4.457 million people (9.0%), about four in ten of all Kims.

You cannot tell which Kim clan someone belongs to from their name, their Hanja or their hometown. You ask. Below: the census numbers, the main Kim clans side by side, how a Korean (or someone with Korean parents) finds their own bon-gwan, how to read a jokbo, and the exact Korean for answering 본관이 어디세요? ("What is your bon-gwan?").

Watch the episode (6:40): Korean Last Names: Why So Many Koreans Are Named Kim. One in five Koreans is named Kim (10.7 million people in the government's 2015 count), and five surnames cover more than half the country.

Why so many Koreans are named Kim: three reasons, with numbers

1. Two royal houses were Kims. Silla's throne was held by the Seok line until the people installed Michu, a Seok king's son-in-law and the first Kim king, after which "the royal line passed to the Kims for a long time," as the National Institute of Korean History puts it. Silla went on to unify most of the peninsula. Geumgwan Gaya, the kingdom based in today's Gimhae, was also ruled by Kims descended from King Suro. When its last king, Guhae (구해왕, also written Guhyeong), surrendered to Silla in 532, his family was taken into the Silla aristocracy. His great-grandson was the general Kim Yu-sin.

2. Late adopters copied the big clans. Many Koreans did not have surnames until relatively recently. The Encyclopedia of Korean Culture's entry on surnames says that into the 15th and 16th centuries slaves and other low-status people made up "roughly half of the whole population", and they had no surnames. As surnames spread down the social ladder, people "imitated large clans such as Kim, Lee and Park," and the most prestigious clans gained the most newcomers attaching themselves to the line (투탁, t'ut'ak). Genealogies were bought, sold and forged on a large scale in the process, the National Institute of Korean History notes.

3. The law made it universal. From 1909, when the new civil registration law (민적법) took effect, the encyclopedia says, "everyone was required by law to have a surname and a bon." Anyone still without one had to register one, and the encyclopedia describes the same pull towards the big clans.

The result is concentration at the top. In 2015 the top ten surnames covered 63.9% of Korean nationals, the top 50 covered 94.2%, and Kim alone was 21.5%. The clans have kept growing: the encyclopedia's table from the 1985 census put Gimhae Kim at 3.767 million and Gyeongju Kim at 1.523 million, against 4.457 million and about 1.8 million in 2015.

So "one in five Koreans is a Kim" is not a myth. It is the 2015 census rounded. What is a myth is that those 10.69 million people are one family.

Gimhae Kim, Gyeongju Kim, Gwangsan Kim: how to tell which Kim clan is which

In the 1985 census (the latest year with per-surname counts we could find), Kim had 285 bon-gwan, more than any other surname, according to the encyclopedia. Lee had 241 and Park 128. Most Kims belong to one of three. On the 2015 figures, Gimhae, Gyeongju and Gwangsan Kims together are roughly two-thirds of all Kims (our calculation from the census shares).

What does not tell you the clan:

• The Hanja. All three clans write 金. Unlike some surnames that split by character, Kim does not.
• The romanisation. Kim, Gim and Ghim are family spelling choices, not clan markers.
• Where someone is from. A bon-gwan is not a birthplace. A Seoul family three generations deep can be Gimhae Kims; the bon-gwan names the ancestral seat, not the address.

What does tell you:

• Asking. This is normal among Koreans, especially older ones, and it is the only reliable method.
• A shared generation syllable. Many clans assign a generation name (항렬자, hangnyeolja): brothers and cousins of the same generation share one of the two syllables of their given name, according to the encyclopedia's entry on hangnyeol. Two Kims with the same syllable in the same slot may be the same clan and branch. Branches often use different syllables, so it is a hint, not proof.

The two origin stories are worth knowing because Koreans tell them. In the Gimhae Kim story, Suro founded Geumgwan Gaya in AD 42, the date the encyclopedia gives. His queen, Heo Hwang-ok, arrived by sea; the Samguk yusa calls her a princess of Ayuta in India, a detail the encyclopedia thinks was probably embellished after Buddhism reached Korea. She is the founding mother of both the Gimhae Kim and the Gimhae Heo clans. In the Gyeongju Kim story, a golden chest is found hanging in a tree in a forest at the Silla capital. A boy comes out, King Talhae raises him and names him Kim, "gold," because of the chest. The Samguk sagi dates this to AD 65. Michu, Silla's first Kim king, was his seventh-generation descendant, the encyclopedia says.

Treat both as clan tradition, not documented biology. A modern Gyeongju Kim is part of a lineage that tells this story; that does not mean an unbroken, recorded chain links every member to Kim Alji.

If you are in Gyeongju anyway, Gyerim is the wood between Cheomseongdae and Wolseong, and our Gyeongju travel guide covers the rest of the old town. Gimhae is next to Busan.

How to find your own bon-gwan

For readers with Korean parents or grandparents, here are the routes, easiest first.

1. Ask the oldest relative. Most Korean families know their bon-gwan, and grandparents usually know the branch (파, pa) as well. Ask "우리 본관이 어디예요?" (uri bon-gwani eodiyeyo?, "What is our bon-gwan?").
2. Read the family register certificate. Korea's family registration law requires each person's register entry to record their name, bon (본), sex, date of birth and resident number. The basic certificate (기본증명서) shows the bon for the person named. Registered Koreans can print it from the courts' e-Family site (efamily.scourt.go.kr) with a Korean certificate login, or get it at a community service centre. Outside Korea, some designated Korean consulates also issue family-register certificates.
3. Find the clan's jokbo. Once you know the clan and branch, the clan association (종친회 or 대종회) usually has the genealogy and can tell you which edition covers your branch. The National Library of Korea holds more than 2,000 jokbo, mostly compiled from the late 1910s to the late 1930s, according to the encyclopedia. National Library materials are for reading on site only, from age 16.
4. See where your clan lives now. Statistics Korea's SGIS map service (sgis.mods.go.kr) has a surname-distribution (성씨분포) map with population by surname and bon-gwan for each city and district, from the 2015 count.

If you are naturalising in Korea, you do not inherit a bon-gwan, but you can create one. Under Article 96 of the family registration act, a new citizen who had a foreign-style surname and wants a Korean surname and bon applies to the family court for permission, then reports it within one month of receiving the certified copy of the permission.

How to read a jokbo (족보)

A jokbo is a clan genealogy, and it is less mysterious than it looks.

The method: find the right branch book, find your branch ancestor, then follow sons generation by generation, using the generation syllable to check you are on the right row. Each entry records more than a name, and what it records depends on the era. Early jokbo such as the 1476 Seonghwabo list children in birth order, daughters included. Late-Joseon patrilineal jokbo add each man's father-in-law and the couple's birth and death years and grave sites, details the family needed for ancestral rites.

Three cautions. Older jokbo are written in Hanja, so names may not match the Hangul spelling a family uses today. Many omitted daughters' descendants, or listed only daughters themselves. And the National Institute of Korean History notes that jokbo were widely bought, sold and forged as commoners were added to them in the colonial period. The oldest surviving jokbo with a genealogy section is the Andong Gwon clan's Seonghwabo of 1476. Most families' records are far younger than the founder story they open with. For how families use these records at the ancestral table, see our guide to jesa and Chuseok rites.

What to say when someone asks 본관이 어디세요?

You will hear the question most from older Koreans, at weddings and family events, and whenever two people with the same surname meet. It is friendly curiosity, not a status check. Answer with the clan name followed by ssi (씨), which here means "clan."

What to avoid: do not ask a new acquaintance their bon-gwan as an opening line, and do not treat a royal founder story as a sign of rank. Do not assume two colleagues named Kim are related. In practice, "Mr. Kim" can be genuinely ambiguous, so confirm a full name, phone number or booking reference when arranging to meet someone. Titles and relationship words do more work than surnames in Korean; our Hangeul and honorifics guide covers them.

Can two Gimhae Kims marry? The old ban and the law now

Yes. For centuries they could not, and the rule lasted into modern law. The ban on marriage between people of the same surname and bon-gwan (동성동본 금혼) dates to Joseon, with an earlier 1309 order under King Chungseon of Goryeo that applied to civil and military yangban, according to the encyclopedia. It became Article 809(1) of the Civil Code. Couples caught by it could only register their marriages during temporary special-law windows: the first opened for 1978 under a 1977 act, and similar laws followed in 1988 and 1996.

On 16 July 1997 the Constitutional Court (case 95Hun-Ka6) held the ban nonconforming to the Constitution and said it could not be applied after 31 December 1998. The Civil Code was then amended in 2005, in force from 2008. Article 809 now bars marriage only between blood relatives within the eighth degree (8촌), regardless of surname or bon-gwan. Two Gimhae Kims who are not close relatives can marry. Some older relatives may still feel strongly about it.

Kim or Gim? Spelling a Korean surname

Under South Korea's Revised Romanization, 김 is written Gim, 이 is I and 박 is Bak. Almost every family still uses Kim, Lee and Park, which became the customary spellings long before the 2000 system. Revised Romanization standardises road signs, place names and textbooks. It does not rename people. Use a name the way the person writes it. If you want to read Korean names directly rather than guess from English spellings, learning Hangul takes an afternoon; our Hangeul design guide shows how the alphabet works on the page.

FAQ

Q: What are Korean clans?

A Korean clan is a descent group identified by surname plus bon-gwan, the ancestral seat: Gimhae Kim, Miryang Park, Jeonju Lee. The 2015 census counted 36,744 such combinations, but the 858 clans with 1,000 or more members cover 97.8% of Korean nationals.

Q: What percentage of Koreans are named Kim?

21.5% of Korean nationals in the 2015 census, 10.69 million people, roughly one in five. Lee was 14.7% and Park 8.4%. The 2015 tables are the latest published surname count.

Q: What is the largest Kim clan?

Gimhae Kim, with 4.457 million people (9.0%) in 2015. It is the largest clan of any surname in Korea, ahead of Miryang Park (3.104 million) and Jeonju Lee (2.632 million). Gyeongju Kim is the second-largest Kim clan at 3.6%, about 1.8 million.

Q: Are Gimhae Kim and Gyeongju Kim related?

Not by clan tradition. Gimhae Kims trace themselves to King Suro of Geumgwan Gaya; Gyeongju Kims to Kim Alji of Silla. After Gaya's last king surrendered to Silla in 532, his family entered Silla's true-bone aristocracy and was called the "new Kims" (신김씨) to tell them apart from Silla's royal Kims. They count as separate clans.

Q: How do I find my bon-gwan?

Ask an older relative, or check the "본" entry on your Korean basic certificate (기본증명서) from the e-Family site or a community service centre. Then find your clan association's jokbo for your branch.

Q: Can people with the same surname and bon-gwan marry in Korea?

Yes. The blanket ban was ruled nonconforming by the Constitutional Court in 1997. Since the 2005 Civil Code amendment, only blood relatives within the eighth degree are barred.

Q: Should it be Kim or Gim?

Use the person's own spelling. Gim is the Revised Romanization; Kim is what most families use.

Sources

• Statistics Korea, Complete Enumeration Results of the 2015 Population and Housing Census (English release): 5,582 surnames (1,507 with Hanja, 4,075 without), 153 with 1,000+ people, top 10 at 63.9% (64.1% in 2000), top 20 at 77.8%, top 50 at 94.2%, 36,744 bon-gwan, 858 with 1,000+ members covering 97.8%, top 10 bon-gwan 35.7%, Gimhae Kim 4,457 thousand (9.0%), Miryang Park 3,104 thousand (6.2%), Jeonju Lee 2,632 thousand (5.3%), 49,706 thousand Korean nationals. Statistics Korea (PDF)
• Asia Economy, reporting the Statistics Korea release (7 September 2016): Kim 1,069만 (21.5%), Lee 730만7000 (14.7%), Park 419만2000 (8.4%), the 2015 top-10 bon-gwan shares including Gyeongju Kim 3.6% and Gwangsan Kim 1.9%. Asia Economy
• Encyclopedia of Korean Culture (Academy of Korean Studies), 성씨 (surnames): half the early-Joseon population without surnames, copying large clans, 투탁, the 1909 civil registration law, 1985 census bon-gwan counts (Kim 285, Lee 241, Park 128) and the 1985 top-10 clan table. encykorea.aks.ac.kr
• Encyclopedia of Korean Culture, 김알지 (Kim Alji), 경주 계림 (Gyerim), 수로왕 (King Suro), 구형왕 (King Guhyeong/Guhae), 김유신 (Kim Yu-sin), 허황옥 (Heo Hwang-ok). Kim Alji, Gyerim, King Suro, King Guhyeong, Kim Yu-sin, Heo Hwang-ok
• Encyclopedia of Korean Culture, 족보 (jokbo) and 항렬 (generation names): daedongbo and pabo, entry contents, the 1476 Andong Gwon Seonghwabo, 2,000+ jokbo at the National Library of Korea, generation syllables. Jokbo, Hangnyeol
• Encyclopedia of Korean Culture, 동성동본불혼 (the same-surname, same-origin marriage ban): 1309 order, Joseon origin, special laws of 1977, 1988 and 1996, the 1997 decision and the 2005 amendment. encykorea.aks.ac.kr
• National Institute of Korean History (우리역사넷): jokbo compiled in earnest from the 16th century, most yangban families by the 17th–18th, commoners added in the colonial period, buying and forging of jokbo. contents.history.go.kr
• National Institute of Korean History: Michu as the first Kim king of Silla. contents.history.go.kr
• Constitutional Court of Korea, 95Hun-Ka6 (16 July 1997), same-surname same-origin marriage ban. english.ccourt.go.kr
• Act on the Registration of Family Relations, Article 9(2) (name, bon, sex, birth date and resident number recorded) and Article 96 (new citizens' surname and bon). Article 9, Article 96
• Supreme Court of Korea, e-Family (전자가족관계등록시스템), certificate issuance. efamily.scourt.go.kr
• Statistics Korea SGIS surname-distribution (성씨분포) bon-gwan population data, reference date 31 December 2015, via the public data portal. data.go.kr