Kim Jae-joong

Kim was born Han Jae-joon (한재준; 韩在俊) in Gongju, South Chungcheong Province, South Korea. His real birthday, as revealed by his biological mother, was on February 4, instead of January 26. At a young age, he was given up for adoption by his biological mother to the Kim family, and his name was changed to Kim Jae-joong. On November 21, 2006, a man with the surname Han filed a lawsuit against Kim's guardians. Han claimed he was Kim's biological father, and thus wanted parental rights. Han cited the reason for the lawsuit against Kim's legal guardians as "for not going through the proper procedures before registering [Jaejoong] in [the legal guardians'] custody." The first hearing was to be held in Kim's hometown, Gongju, on November 29, 2006, but on November 22 Han dropped the charges against Kim's legal guardians. In reaction to the matter, Kim uploaded a journal entry on his official fan club website, and said that he was informed of the existence of separate biological parents by his mother two or three years ago, and it had been quite a shock to him. With his adoptive mother's support, his biological mother was able to keep in touch with him, and to meet occasionally, but whereabouts of his father had been unknown. He expressed his will to live by the name of Kim Jae-joong, not by his birth name Han Jae-jun (한재준).

When Kim was fifteen, he moved to Seoul by himself in order to take part in the auditions held by SM Entertainment. Life in Seoul was financially difficult and he took various odd jobs to pay for rent, food, and training fees; and even appeared as an extra in movies. In an interview, he admitted he used to be tone-deaf in primary school and was frequently ridiculed for his dream of becoming a singer, but managed to overcome it through practicing alone.

Kim attended Gongju Jungdong Elementary School (중동초등학교), Kongju National University Middle School (공주대학교 사범대학 부설중학교), Kongju Information High School (공주정보고등학교) and then dropped out in 2001. He enrolled Hanam High School (하남고등학교) in 2005 and Kyung Hee Cyber University (경희사이버대학교), majoring in Digital Media Engineering.Prior to his debut as a singer, Kim worked as an extra, playing a soldier in film Taegeukgi. Along with the other members of TVXQ, he acted in television programmes, Banjun Theater and Vacation.

In November 2009, Kim co-starred with Han Hyo-joo in the joint Korean-Japanese telecinema Heaven's Postman as a young man who delivers letters written by the living to the dead and helps lingering ghosts settle their earthly affairs. This was followed by a leading role in Fuji TV's Japanese television drama Sunao ni Narenakute in September 2010. In August 2011, he starred in his first South Korean television series, Protect the Boss with Choi Kang-hee and Ji Sung. He played the role of seemingly a perfect director known for his business acumen, who becomes frustrated and fight against the constraints in his life.

In May 2012, he starred in historical fusion drama Dr. Jin with Song Seung-heon. He played the role of a high-ranking officer of the police force of Joseon Dynasty, who is an illegitimate son of the Joseon era's Prime Minister and his concubine. This was his first time acting in a sageuk, and he was praised for his performance. The same year, Kim made his big screen debut in the action comedy film Jackal is Coming playing a Hallyu star who is kidnapped by an assassin (played by labelmate Song Ji-hyo). His comical acting in the film drew positive reception from fans.

In May 2014, Kim starred in MBC's drama Triangle as a man who grows up to become a lowlife gangster. His performance won the "Top Excellence Award, Actor" at the 7th Korea Drama Awards in October the same year. In January 2015, Kim starred in KBS2's thriller SPY as a genius analyst working for South Korea's National Intelligence Service. The drama is based on the Israeli drama The Gordin Cell, modified to depict North/South Korean relations. In 2017, Kim was cast in KBS2's time-slip drama Manhole, as a man who travels back and forth through time to stop a wedding from taking place.

For the first time in 10 years, Kim returned to entertainment shows in South Korea with his appearance as a panelist for season 2 of Taste of Love in 2019. In 2020, Kim hosted a travel series where he ventured to Argentina alone to befriend strangers for Lifetime Korea's Travel Buddies which aired 10 episodes from February 8, 2020, to April 2, 2020. During a press conference, Kim stated, "We all shared similar worries. We mostly talked about the ways to unfold our life and attain goals. I believe many viewers would empathize with us. Through the conversations, I reflected upon my bygone days and deeply thought about my future. Thus, the trip was not merely about playing and entertaining to me". Kim is filming season 2 of Travel Buddies which will take place in South Korea. The airing is scheduled from the end of April to the beginning of May 2021. On March 29, 2021, Kim debuted his 6-episode variety show called ジェジュンＪ! (Jaejoong J!) which was broadcast in Japan on channel BS SKY PerfecTV.

In the summer of 2021, Kim will have a documentary released about his life and career called Jaejoong: On the Road, directed by John H. Lee. In 2022, Kim was cast as the lead male role in the Korean television drama Bad Memory Eraser co-starring Jin Se-yeon. He guest starred in the third episode of the television adaptation of the manga Waru - Who said it's not cool to work?, for which he also sang the theme song.

Kim served as executive director for the Asian leg of JYJ's 2011 Worldwide Tour. He also participated in the directing team for the 2011 LG Whisen Rhythmic All Stars.