These are the Korean celebrity siblings and relatives that I know of. If you guys know any more, you can share.
SS501 member, Kim Hyung Joon and former Xing member, Kim Ki Bum a.k.a. Marumir are brothers. Kim Ki Bum left Xing in 2007; now he is in a new boyband named U-Kiss.
Kim Ki Bum:
SS501 member, Kim Hyung Joon:
Korean actor, Lee Joong Moon (he starred in the Korean drama called "18 Vs. 29" with Ryu Soo Young and Park Sun Young) has a relative in the Korean entertainment industry. Her name is Lee Yo Won and she starred in "Fashion 70's". I found this information from soompi and later found out that they're cousins.
Lee Joong Moon:
Lee Yo Won:
Korean actor, Uhm Tae Woong and Korean actress/singer, Uhm Jung Hwa are siblings.
Uhm Tae Woong - he starred in the Korean drama called "Sassy Girl, Chun Hyang".
Uhm Jung Hwa:
Korean actor, Lee Wan (real name is Kim Hyung Soo) and Korean actress, Kim Tae Hee are siblings.
Kim Tae Hee:
Korean actor, Shin Dong Wook and Super Junior member, Kim Ki Bum are cousins. Here is information from DramaWiki: Click here
Shin Dong Wook - he starred in the Korean drama called "Cloud Stairway".
Ha Ji Won has a younger brother name Jeon Tae Soo and he starred in the drama called "A Good Day For Love" (translation: ?사랑하기 좋은 날?). This is her younger brother's debut drama. Ha Ji Won's real name is Jeon Hae Rim.
The late Korean actress, Choi Jin Shil has a younger brother name Choi Jin Young who is a singer.
Choi Jin Shil committed suicide and her body was found hanging in her bathroom at her home in Jamwon-dong in Seocho-gu, Seoul. Choi Jin Shil had been rumored to have lent money to actor Ahn Jae Hwan who also committed suicide last month.
Nathan Lee from the Korean boyband called "Take" and Joanne are siblings.
Here are pictures of Korean singer, Joanne.
Former G.O.D. members, Danny Ahn and Park Joon Hyung are cousins. G.O.D. stands for Groove Overdose. G.O.D.'s biography on KBS WORLD reveals that they're cousins.
Park Joon Hyung:
Shinhwa member, Kim Dong Wan & Kwon Sae Eun from Akdong Club are cousins.
Kwon Sae Eun from the Korean boy band called Akdong Club. He apparently got arrested for assaulting & threatening his ex-girlfriend. Got this information from soompi.
Kim Dong Wan from Shinhwa:
BoA and her 2 oppas or older brothers.
Kwon Soon Hwon released two classical albums.
Kwon Soon Wook is a music video director and works with jewelry brand Ramee and BB Simon.
Here's an article I've found:
The Kwon siblings, Soon-hwon, Soon-uk and BoA, are very supportive of each other.
In fact, Kwon Soon-uk (27) directed the music video of the ?Laprimo? digital album of pianist Kwon Soon-hwon (28).
Although BoA and her 2 older brothers have different fields they work in, they still manage to help and support each other. Like last year, BoA returned to Korea from Japan to attend the launching of her brother Kwon Soon-uk?s fashion accessories business. Her other brother, Kwon Soon-hwon, showed her support for his sister and did a piano performance during BoA?s showcase.
Kwon Soon-hwon is currently preparing to enter the Royal Academy of Music in London, which is one of the world?s leading music schools. Aside from directing music videos, Kwon Soon-uk has also expanded his business into the jewelry brand Ramee, which will be available at the Lotte Young Plaza in Myeongdong.