In 1956, Lansdowne's sister Lady Caroline Petty-Fitzmaurice died in a shooting accident, aged seventeen. On 18 February 1965, his mother also died from shotgun injuries in the gunroom at her Scottish home,
Meikleour House, which was also found to have been an accident. On 9 October 1965, as Lord Shelburne, he married Lady Frances Helen Mary Eliot (6 March 1943 – 6 January 2004), daughter of
Nicholas Eliot, 9th Earl of St Germans; they were divorced in 1987, having had four children: • Lady Arabella Helen Mary Petty-Fitzmaurice, now Lady Arabella Haldane Unwin (born 1966), married Rupert William Haldane Unwin, and has three children. • Lady Rachel Barbara Violet Petty-Fitzmaurice (born 1968), married James Spickernell and has four children. Subsequently, Lansdowne married secondly
Fiona Mary Merritt (born 1954), daughter of Donald Merritt and Lady Davies, She was appointed a
Deputy Lieutenant of Wiltshire in 2019, and as
High Sheriff for 2022–2023. She is one of the official
Queen's companions to
Queen Camilla. The
heir apparent to the peerages is Simon, Earl of Kerry (born 1970). ==Honours and arms==