Why was Sung Shi Kyung jealous of Kim Tae Woo?

Singer Sung Shi Kyung confessed that at one point in time, he was really jealous of Kim Tae Woo. But what was the reason? The singer was a special guest on 'Choi Hwa Jung's Power Time' radio program on March 21st, and through it, he talked about his past in the military. He revealed that he was very jealous of Kim Tae Woo when both of them were in the military because he himself possessed a quiet voice while Kim Tae Woo had a strong, loud voice; in the end, that difference resulted in Kim Tae Woo making a better impression on higher-ranking soldiers. Sung Shi Kyung had also confessed that he was a great fan of�IU's, who was also a guest on the show.�Sung Shi Kyung admitted that during his time in the military, IU was not only his addiction, but the addiction of every soldier on base. Source: MyDaily