Older Sister born Seoul, Korea 1962-1964, Lastname Chung

I'm looking for my older sister. I don't know her first name. Our last name was translated to Chung (which is not a very common Korean name - more Chinese, so there may have been a mistake at INS). My full name was translated into Chung Un Young. We were both born in or around Seoul, Korea but adopted to different families. I think she was adopted to a Korean family. I was adopted by an American Air Force Major and Korean wife. I was adopted in 1974 when I was about 7 yrs old. I was born in September 1966. My older sister was about 3 years older born maybe between 1962 -1964. My older sister was adopted before me maybe in 1972 or 1973. We lived with our grandparents before then. Our grandparents farmed. I think we have 3 aunts and 1 uncle. Our grandfather died about 6 months after I was adopted in 1974. I think our birthmother died maybe 1971 or 1972. I don't know anything about our biological father. I believe we are both full-blooded Korean. I have no known genetic disorders that was passed on. Please contact me if you think this is you or if you know someone missing a younger Korean sister.