왕자님 오디오 북 《사운드 오브 왕자님》) Roe Although born in 1971, he looks younger than his actual age, and that is why many fans of Um tend to call him 상현소년 (Sang-hyun-so-nyeon) meaning "The Boy Named Sang-hyun", or its shortened form, 상현손 (Sang-hyun-son).
Meskipun lahir pada 1971, ia terlihat lebih muda ketimbang usia sebenarnya, dan hal itulah yang menjadi penyebab kenapa beberapa penggemar Um memanggilnya 상현소년 (Sang-hyun-so-nyeon) yang artinya "Anak Laki-Laki yang Bernama Sang-hyun", atau disingkat 상현손 (Sang-hyun-son).