Legge-Bourke's brother Harry, born in 1972, was a Page of Honour to Queen Elizabeth II between 1985 and 1987 and became an officer in the Welsh Guards.
In 1966, Legge-Bourke's grandmother Margaret Glenusk, widowed in 1948, married secondly William Sidney, 1st Viscount De L'Isle, who had been Governor-General of Australia from 1961 until 1965.