Related Information for Jessica & Krystal Jessica Jung (제시카 , born April 18, 1989) is an American-born Korean singer, dancer and actress. She's one of the lead vocalists of a girl group Girls' Generation (소녀시대).Jessica's younger sister Krystal Jung (크리스탈, born October 24, 1994) is an American-born Korean singer and model. She's one of the lead vocalists of a girl group f(x).During SMTOWN '10 Live Tour in Seoul they covered Ke$ha's hit song TiK ToK... read more