In Gyo-jin was born in Jochiwon, Yeongi County, South Chungcheong Province (now Sejong City).

In made his acting debut in 2000, first appearing in the long-running television series Lifetime in the Country.

Early in his career, his then-agency proposed that he use a stage name, and he was known as Do Yi-sung (Korean: 도이성) until 2011.

[6] In and So had been friends for a decade before dating; they were costars in Fairy and Swindler (2003), Aeja's Older Sister, Minja (2008) and Happy Ending (2012).

[10] In Gyo-jin and his daughter were cast members of the KBS2's variety show The Return of Superman.