You're Beautiful (2009)

The management company of the idol group A.N.JELL insisted on adding a new singer to the group as the lead vocal, Tae Kyung's voice was hurting. However,the new member, Mi Nam, had to go to the States to repair a botched eye job just before signing the contract. His agent came up with the idea of having his twin sister, Mi Nyu,to stand in for him and pretend that she was her brother. The two of them grew up in an orphanage and Mi Nyu, who was all set to become a nun, agreed to this charade as she didn't want to spoil her brother's chance of fame which would make it easier to look for their mother.