He was born on 18 April 1962 in Nuwara Eliya as the youngest of the family with two elder sisters – Niranjali Sunethra and Nirmali Savithri. His father Piyasena Witharana was a Local Government Officer and mother Nalini Decibel Jayasuriya was a housewife. He lived in Nuwara Eliya from 1962 to 1967 and then moved to Kandy until 1972. In 1968, he entered primary section of Dharmaraja College, Kandy and then entered St. Thomas' College, Matale from grade 6. In 1986, he moved to Colombo with the family and in 1992 permanently resides in Kamathawatte, Rajagiriya.

 

On 6 January 1976, when Dayan was 13 years old, his father died at the age of 54 by a heart attack. After his father's demise, his mother started a cookery class and a needlework. His mother suffered from cancer for many years where she died on 25 April 2006. Former parliamentarian Gamini Jayasuriya is the cousin of Dayan's mother.

 

Dayan is single, and he said he will not marry in the future as he is living according to the principles of Buddhism.