Question: In what year was the South Korean boy group whose leader is Kang Seung-yoon formed?
Sentence (from "Kang Seung-yoon"): Kang Seung-yoon (born (1994--) 21, 1994 ), known as Seungyoon, is a South Korean singer-songwriter, record producer, actor, and leader of boy group Winner.
Relevant evidence: Yes