Question: Of which boy band was the headliner for Triangle an original member?
Sentence (from "Kim Jae-joong"): Kim Jae-joong (Hangul: 김재중 ; Hanja: 金在中 ; born January 26, 1986), also known mononymously as Jaejoong, is a South Korean singer, songwriter, actor, director and designer.
Relevant evidence: No