Carysfort was the fourth son and youngest child of Admiral Granville Proby, 3rd Earl of Carysfort, and his wife Isabella (née Howard), who died only four days after his birth.
[1] He was commissioned as a Captain in the part-time Wicklow Militia on 16 May 1861, retiring on 26 March 1872.
In 1872 he succeeded his elder brother in the earldom and entered the House of Lords.
He owned almost 26,000 acres in Counties Wicklow, Northampton, Dublin and Kildare.
[3] Lord Carysfort married Charlotte Mary, daughter of Reverend Robert Boothby Heathcote, in 1860.