De Alwis was born on 3 June 1947 in Colombo, Ceylon. He was the second child of Simon de Silva, a railway employee from Maradana. He was educated at Maradana Maligakande Maha Vidyalaya and Ananda College where he co-edited the school newspaper Dhamma Jayanthi and compiled the Anandaya magazine in 1965.

 

In 1961 he unsuccessfully auditioned to be a singer on Radio Ceylon. However, his speaking skills enabled him to take part in several children's radio programmes, including Lama Pitiya and Lama Mandapaya, presented by Karunaratne Abeysekera.

 

De Alwis had two children – a daughter (Surangi) from his relationship with Daya de Alwis, and a son (Poorna Sampath) from his relationship with Nirmala de Alwis.

 

De Alwis father wanted him join the railway department but de Alwis was attracted to radio broadcasting. De Alwis joined the Visithura magazine, part of the Davasa group, in 1966 as a feature writer. He started working for Radio Ceylon as a freelance announcer on 17 December 1967. He became a permanent announcer in June 1971 and was promoted to programme producer. He became a Grade Two announcer in 1974 and afterwards presented programmes such as Sonduru Sevana, Serisara Puvath Sangarawa and Shanida Sadaya on Radio Ceylon's successor Sri Lanka Broadcasting Corporation (SLBC). He later joined the Sri Lanka Rupavahini Corporation, presenting programmes such as Anduna, Sanidtha Ayubowan and Sampath Rekha (National Lotteries Board).

 

De Alwis was a prolific lyricist, writing hundreds of songs. He wrote his first song, Hada Puda Asune Senehasa Bendune, in 1969 for Rupa Indumathi and Malkanthi Nandasiri. In the same year he wrote his first film song, for Lokuma Hinawa directed by K. A. W. Perera. He wrote songs for more than 150 films. He wrote songs for numerous singers including Mohideen Baig, Malini Bulathsinhala, Milton Mallawarachchi, J. A. Milton Perera, Mervyn Perera, Victor Ratnayake, Freddie Silva and Priya Suriyasena.

 

Popular songs written by de Alwis include Aaron Mama, Adaraneeya Neranjana, Adare Ran Bingun Nesu, Beri Bara Hindai Daruwan Dunne, Eda Re Guwan Thotupoledi, Eka Gini Koorai Mulu Gedarama Thibune, Kurullanta Gee Gayanna, Ma Ekkala Amanapawa Wee Dabara, Mannaram Piti Welle, Me Nagaraya, Mudu Parama Supiwithuru, Oba Dedunna Akasaye, Raththaran Menik Muthu Mokatada Ewa and Sanda Midulata Enawa.