Seoirse was born in 1894, in Dublin,[REF] where his parents lived at the time, the son of George Noble Plunkett, a papal count and curator of the National Museum and his wife, Josephine, née Cranny; the Plunkett and Cranny families were both housing developers.
George was named after his father and his collateral ancestor Oliver Plunkett, Archbishop of Armagh, who was martyred in 1681.