Ký was born on December 22nd, 1928. Ký's father was Hồ and his mother was Can Nguyễn Hữu. His paternal grandparents were Mạnh Cung and Hoan (Loan) Đỗ. He has two brothers and three sisters, named Ban, Hoan, Bột, Bật and Tham. He is the youngest of the six children.