Seo Taiji & Boys was formed in 1991 with Seo Taiji, Lee Joono and Yang Hyun-Seok. The group was influential on the Korean music scene, famous for their single, "Nan Arayo" (Hangul: "난 알아요", "I Know"). The group received criticism for various albums, most notably for the song, "Shidaeyugam" (Hangul: 시대유감, "Regret of the Times"), to which the fan out lash led to the abolishment of the Pre-censorship law in 1996. The group disbanded in 1996, with each member pursuing solo activities.
In March 2010, Yang revealed that he has been dating former Swi.T member Lee Eun-ju, who is 12 years Yang's junior, for nine years. Lee Eun-ju then gave birth to their first child on August 5, 2010 at 2:01 pm and is named Yang Yoo-Jin. In April 2012, Yang Hyun Suk announced on SBS K-pop Star that the couple's second child, a baby boy, was born.