It is thought that Ko and Kim Jong-il first met in 1972. In 1981, Ko gave birth to son Kim Jong-chul, her first child with Kim. It was Kim's fourth child, after daughter Kim Hye-gyong (born 1968 to Hong Il-chon), son Kim Jong-nam (born 1971 to Song Hye-rim), and daughter Kim Sol-song (born 1974 to Kim Young-sook). Kim Jong-il's second child with Ko, the present North Korean supreme leader Kim Jong-un, followed one to three years after Jong-chul. Their third child, Kim Yo-jong, a daughter, was believed to be about 23 in 2012. However, the birth year of Kim Yo-jong is also given as 1987.