[1] He was the only son of Dive Downes, Bishop of Cork and Ross, and his fourth wife Catherine Fitzgerald, daughter of Honorable Robert FitzGerald and his wife Mary Clotworthy, and sister of Robert FitzGerald, 19th Earl of Kildare.
Robert married Elizabeth Twigge, daughter of Thomas Twigge of Donnybrook, and had two sons, Dive (died 1798), a clergyman, and William Downes, 1st Baron Downes (1751-1826), Lord Chief Justice of Ireland, as well as at least two daughters.
[2] Downes sat in the Irish House of Commons as the Member of Parliament for Kildare Borough from 1735 to his death in 1754.
[3] He lived at Donnybrook Castle, County Dublin.
His death was agreed to be accidental, due to running himself through with his own sword.