On 7th of March 2015, Ki got married to Hayoung Choi. His wife, Hayoung Choi is also an actress and she has appeared in the short film She Has a Boyfriend where she played the role of Ki's girlfriend. They are happily married. Ki is now aged 29 years old and his height is five feet and nine inches tall. His nationality is South Korean as well as American.
While Ki was in his middle school he also active in church skits. There he appeared in several plays and induced his interest in acting from that time on. After his high school graduation in 2004, he joined University of California, Berkeley with a major in psychology. There he also took part in Liberty in North Korea chapter. He earned his undergraduate degree in 2008. In 2010, he appeared in several TV series like Victorious, The Secret Life of the American Teenager and Modern Family. He made his stage debut in 2011 by starring the role of Jason in the play Wrinkles. That year he also appeared in the short movie All in All. His breakthrough role as an actor came in 2014 after he starred the role of Minho in an American neo noir dystopian science fiction action thriller film The Maze Runner. His net worth is 4 million dollar.