Rajanarayanan was born on 16 September 1923 in Idaiseval village near Kovilpatti in present-day Thoothukudi district, Tamil Nadu. He was the fifth child of Lakshmi Ammal and Shri Krishna Ramanujam. He suffered from poor health and was afflicted with tuberculosis at an early age. He dropped out of school in the seventh standard. He went on to become a member of the Communist Party of India (CPI), going to prison twice for his participation and support in the CPI-organised peasant rebellions between 1947 and 1951. He was also named in the "Nellai Conspiracy Case" of 1952, though the charges were later dropped.