Proby was born at Bushey Park, Enniskerry, County Wicklow, the second son of Admiral Granville Leveson Proby, 3rd Earl of Carysfort, by Isabella Howard, daughter of the Honourable Hugh Howard.
Born in Bushey Park, Enniskerry, County Wicklow, Proby was the second son of Admiral Granville Leveson Proby, 3rd Earl of Carysfort, and Isabella Howard, daughter of the Honourable Hugh Howard.