Twin sisters looking for birth mother Choi, Jung-Hee (b. 1945) from Seoul

Hi- I am searching for my birth mom Choi, Jung-Hee, born 1945. My sister and I (Cho, Ok Sun and Cho, Ok Mi) were adopted in 1976 from Seoul through what was called David Livingston at the time. Our birth father was named Cho, Young-Won, also born in 1945, but we've been told he died in 1995. Our parents were married and we have three older brothers, who were 10, 8, and 3 at the time of our adoption in 1976. One of our brothers is said to have moved to Japan with his wife. If you know any information, please contact me. Thanks!