Martin was born in 1960 in Cork, and was raised in the Turners Cross area. Martin was the son of Paddy Martin (1923–2012), a former soldier in the Defence Forces, CIÉ employee and Irish international boxer, and Eileen "Lana" Corbett (1929–2010). He was the third child in a family of five. Martin's eldest brother Seán and his twin brother Pádraig subsequently became involved in local politics in Cork. His two younger sisters, Eileen and Máiréad, have remained apolitical. Martin attended Coláiste Chríost Rí before studying arts at University College Cork.