Approximately 20% of Korea's population carries the surname 'Kim.' From a foreigner's perspective, they might all appear to belong to one giant 'Kim family.' However, for Koreans, asking "Which Kim are you from?" is a far more meaningful question than "Are you a Kim?" This is because, while the spelling and pronunciation are identical, not all Kims are the same Kim. The key to this secret lies in **Bon-gwan (본관)**.
What is Bon-gwan (本貫)?
Bon-gwan, simply put, refers to the 'hometown where the progenitor (始祖) first settled,' in other words, the root region of that surname. Korean surnames are not identified by the surname alone; a complete identity is formed only when the surname and Bon-gwan are combined. Therefore, even if individuals share the same surname, if their Bon-gwan differs, they are recognized as completely different families.
Gimhae Kim vs. Gyeongju Kim: Different Roots, Different Stories
The most prominent examples are Gimhae (金海) Kim and Gyeongju (慶州) Kim. While both are among the most populous Bon-gwan in Korea, their roots are entirely different.
- Gimhae Kim (金海 金氏): They venerate King Suro (金首露王), the progenitor of Gaya, as their ancestor. According to legend, he was born from a golden egg descended from heaven.
- Gyeongju Kim (慶州 金氏): They trace their ancestry to Kim Alji (金閼智) of the Silla era. He also has a mystical birth legend, said to have been discovered in a golden box.
As such, these two Kim clans do not consider each other relatives due to their different progenitors and origins. That is, Gimhae Kim and Gyeongju Kim are separate families, not 'the same Kim.' This is similar to how Jeonju Yi and Gyeongju Yi are different for the Yi (李) clan.
Genealogical Records and Branching: Can We Meet if We Go Back Far Enough?
So, are all members within the same Bon-gwan close relatives? Not necessarily. Even within one Bon-gwan, over time, various 'branches (派)' emerge. Following the genealogical records (族譜) backward, these branches eventually converge to a single common ancestor several generations up.
However, the case is different when Bon-gwan differ. No matter how far back one traces the genealogical record of Gimhae Kim, it will not meet the ancestors of Gyeongju Kim. They are like two entirely independent giant trees, with different starting points.
This concept of 'same surname, different families' formed the basis of the past custom of **Dongseongdongbon Geumhon (同姓同本 禁婚)**, which prohibited marriage between individuals of the same surname and Bon-gwan. Because it was believed that all people with the same Bon-gwan were descendants of a single grandfather, marriage was legally forbidden. While Kims with different Bon-gwan could marry, a Gimhae Kim could not marry another Gimhae Kim.
In conclusion, 'Bon-gwan' is an indispensable core element when understanding Korean surnames. Beyond the simple names of Kim, Lee, and Park, the hundreds of Bon-gwan stories hidden reveal how multi-layered and historically deeply connected the Korean identity is.