His youngest brother, Lt.-Gen. Frederick George Slade CB FRGS (15 December 1851 – 16 August 1910) served in multiple campaigns in the late 19th century and was Inspector-General of the Royal Garrison Artillery headquarters 1902–1906.

[4] After taking part in the Bazaar Valley Expedition in 1878, he commanded a battery at the Battle of Maiwand in July 1880 during the Second Anglo-Afghan War.

[4] He served as a staff officer during the First Boer War and then became military attaché in Rome in 1887.

Lady Constantia was the daughter of Col Hon Henry Cecil Lowther (son of the 1st Earl of Lonsdale) and Lady Lucy Sherard (daughter of Philipp Sherard, 5th Earl of Harborough).

[3] Slade was baptised into the Church of England shortly after his birth and again at aged 2,[7][8] but later converted to Roman Catholicism.