D.O. was born in Goyang, Gyeonggi Province, South Korea, on January 12, 1993.[1][2] He went to Goyang Poongsan Elementary School, Baekshin Middle School, and Baekseok High School. He has an older brother, Do Seungsoo, who is 3 years older than him. D.O. began singing in primary school and was an avid participant in local singing competitions throughout his high school career.