Kim Jae Seop, better known by his stage names AJ and Si Yoon, was the vocalist, dancer and composer of the boy group U-KISS. He was also the rapper, vocalist and maknae of the boy group Paran. He is also a model. He appeared in Grey and Verbal Jint's video for the song ''Pretty Brown''. He wrote many U-KISS'songs like: Words that hurt me (together with Dong Ho), Believe, I love you, Love of a Friend, Top That, Obsession and Tell me. He also wrote the rap part for U-KISS' song ''0330''. He used to live in the United States (New York). Edit Biography