Rajkumar was born to Selvarajan and Kannammal. The family ancestors belong to Paettai, Thirunelveli District. His father was a vocalist performing in stage shows conducted by popular music directors such as Ilayaraja, Gangai Amaren, Deva among others. Rajkumar admired his father's musical career and developed an interest in music. It was his mother who encouraged his father to make him join music classes. Rajkumar underwent classical music training under the guidance of Subbaiah Bhagavathar for 3 years