Charles FitzClarence was born in County Kildare, the son of Captain George FitzClarence (15 April 1836 – 24 March 1894) and Maria Henrietta Scott (1841 – 27 July 1912). He had a twin brother named Edward. His paternal grandfather was The 1st Earl of Munster, an illegitimate son of William, Duke of Clarence (later King William IV of the United Kingdom). He joined the Royal Fusiliers in 1886 but his early career was blighted by several bouts of illness and he spent much of his time in administrative and staff roles. In 1899 he volunteered to serve as a Special Service Officer at Mafeking, South Africa and was given the duty of training a squadron of the Protectorate Regiment.