Gemini Ganesan was born Ganapathi Subramania Sarma in 1920. Ramaswamy's father Narayanaswami was the Principal of the Maharajah's College, Pudukkottai. His grandfather died when he was in the sixth class and later on, he lost his father as well. After the death of his father, Ganesan, along with his grandmother Bagirathi and mother Gangamma, moved to his aunt Muthulakshmi's residence, in Madras (now known as Chennai). Life in the city did not suit Gangamma, and she decided to go back to Pudukkottai. His birth name is widely accepted as Ramaswamy Ganesan, though it is also rumoured to have been Ganapati Subramanian Sarma.
He, at 19, married Alamelu, with whom he lived and whom he fondly called "Bobji". She is his first and only legal wife. He later married or had intimate relations though did not live with actresses Pushpavalli and Savitri. He is survived by seven daughters and a son. Alamelu and Ganesan have four daughters; three of them – Revathi, Kamala and Jayalakshmi - are medical doctors, the fourth Narayani is a journalist with The Times of India. Ganesan has two daughters with Pushpavalli – Bollywood actress Rekha, and Radha.
A documentary film on the legend in the name of "Kadhal Mannan" was produced by Dr. Kamala Selvaraj, and directed by Ashok Kumar, DFT (Programme Head-Vendhar TV) in 2011. His end came at 22 March 2005, 13:30 IST at the age of 84 in his residence after a prolonged illness caused by Renal Failure and multiple organ failure. He was cremated with full state honours.
He made his film debut in 1947 with the social satire film Miss Malini, in a minor role. He also starred in Kalathur Kannamma (1959), which was also the debut for Kamal Haasan, who would later become one of the leading actors in Tamil cinema. He also starred in Veerapandiya Kattabomman (1959) alongside Sivaji Ganesan. The film was selected for the Afro-Asian Film Festival in 1960. His 1961 film Then Nilavu was the first Tamil film to be shot extensively in Jammu and Kashmir, and became a great success at the box office. He acted in a few Hindi films, most of which were remakes of his Tamil films. His first Hindi film was Miss Mary in 1957, where he was paired with Meena Kumari. The film became one of the biggest hits of that year.