Background
He was the son of Major Honorary Cyril Myles Brabazon Ponsonby (1881–1915), second son of Edward Ponsonby, 8th Earl of Bessborough, and his wife Rita Narcissa Longfield, daughter of Lieutenant Colonel Mountifort John Courtenay Longfield.
Member of the European Parliament politician
He was the son of Major Honorary Cyril Myles Brabazon Ponsonby (1881–1915), second son of Edward Ponsonby, 8th Earl of Bessborough, and his wife Rita Narcissa Longfield, daughter of Lieutenant Colonel Mountifort John Courtenay Longfield.
He was educated at Harrow School and Trinity College, Cambridge.
Later he rose to the rank of Captain in the service of the Welsh Guards and saw action in the Second World War. Myles Fitzhugh Longfield Ponsonby (born 16 February 1941), later the 12th Earl of Bessborough Lady Sarah Ponsonby (born 1943, died 13 March 2010) Sir Rudolf Carl von Slatin (Baron von Slatin). Laurence Douglas Grand, and together they had two children: Matthew Douglas Longfield Ponsonby (born 27 January 1965), married Jamilie Emett Searle Charles Arthur Longfield Ponsonby (born 12 July 1967), married Jennifer Waghorn.