Kumarasinghe was born on 9 April 1934 in Udamadura village, Rikillagaskada,
Walapane, Sri Lanka. His father, K. S. D. Rajapaksa was a teacher. His mother Weerasinghe Menike was a housewife. He was educated at
St. Sylvester College, Kandy. He had seven brothers including: Wijewardena, Wickramaratne, Premachandra and a sister named Indrani. Among these, Wijewardene Rajapaksa, was involved in cinema, produced the films
Ran Kurullo and
Rathu Makara directed by Kingsley. His brother Premachandra Rajapaksa, was a retired teacher. His son Dhammika Rajapaksa works as a lighting and assistant costume designer for films and teledramas at a Nugegoda Production Company. He was married to his longtime partner, Iranganie Bulathsinhala. He had five children: eldest daughter Saman Rajapaksa who was married to Shantha Karunaratne, son of Prof.
W. S. Karunaratne, former Ambassador of Sri Lanka to the United States of America and Indumathi Karunaratne. Other sons are Chandana and Mangala. Mangala died in 2018. Youngest daughter is Chandrika. Kingsley was ill for several years and left the film industry. He died of a heart attack on 13 June 1983, at the age of 49. ==Career==