Sein Lwin was born on 27 January 1924 in Kawkayin village, Paung, Mon State then under the British Raj to parent Shwe Yin and his wife Ma Ma Gyi.
On January 27, 1924, Sein Lwin was born in Kawkayin village, Paung, within the Mon State region that was then part of the British Empire. His parents were Shwe Yin and Ma Ma Gyi.