Rupert Major Downes was the son of Major-General Major Francis Downes C.M.G. and Helen Maria (Chamberlin) Downes, born 10 February 1885.

He married Doris Mary Robb in 1913 and had three children, Rosemary Major Downes, Valerie Marjorie Downes and John Rupert Major Downes.

Doris travelled to Egypt to visit her husband in March 1917. By June, Rupert was becoming increasingly immersed in preparations for the Third Battle of Gaza and Doris, who had become pregnant during her visit, decided to return home. On her return journey to Australia in June 1917, her ship, the P&O liner Mongolia struck a mine and was sunk in the Indian Ocean with the loss of 23 lives. Doris spent 11 hours in a crowded lifeboat, before being rescued by a passing steamer, which took her to Bombay. From there she eventually made her way back to Australia via Singapore and Batavia. In 1918 Doris was appointed an Officer of the Order of the British Empire (OBE) for her volunteer work among soldiers’ families as secretary of the Friendly Union of Soldiers’ Wives and Mothers

His daughter Rosemary Major (Downes) Campbell was awarded the Medal of the Order of Australia.

He retired from the army a month before his 60th birthday.  Previously after the First World War he was invited to write a chapter for the ‘Official history of the Australian Army Medical Services’. When it was known of his imminent retirement he was again invited to contribute to write the official medical history of Australia during World War II.    

Major-General Downes was killed at Machans Beach, Queensland, Australia. He was on board a Hudson Aircraft, travelling from Archerfield, Brisbane, to Cairns and was killed when it crashed into the sea, near Cairns. Also killed were Major-General Vasey, Lieutenant-Colonel G A Bertram, Flight Lieutenant J W Newell, Flying Officer D J Bassett, Flying Officer F B Frieze, Flying officer G Thompson, Corporal R L James and LAC J D Moore.