The Pedigree of The White Knight was one of three hereditary knighthoods within Ireland dating from the medieval period. It was held by the Fitzgibbon family, and has since become dormant. The others are Fitzgerald: Knight of Glin (also called the Black Knight) which has also become dormant after 700 years, (since the passing of the 29th Knight, September 2011) and Fitzgerald: Knight of Kerry (also called the Green Knight).
The first White Knight was Maurice FitzGibbon, son of Sir Gilbert fitz John, eldest illegitimate son of John FitzGerald, 1st Baron Desmond and Honora, daughter of Hugh O'Connor Don aka Ó Conchubhair Donn of Kerry, King of Connacht aka Felim Ua Conchobair. A kinsman, the Earl of Desmond, acting as Count Palatine, is said to have conferred the title of 'White Knight' on Gilbert as well as the titles of Knight of Glin (or Glynn) and Knight of Kerry on two of Gilbert's brothers. The Knight of Glin is also known as the Knight of the Valley, 'valley' being the English for 'glin' ( this Gaelic word is also the source of the borrowed English word 'glen').
One notable White Knight was Edmund FitzGibbon.
"This Gilbert was of fair hair and complexion, and, being knighted, was called "The White Knight"; and by the Irish Ryther-u-fin. His eldest male descendent were constantly denominated by that title until the time of Queen Elizabeth, when John Og FitzGibbon, the then White Knight, who had taken an active part in the Desmond Rebellions of his kinsman The Earl of Desmond, was attainted by act of parliament, after his death, by the name of John Fitzgerald, The White Knight, or John Og FitzJohn, Knight, FitzGibbon.
The title passed from father to son for nearly three hundred years.
Margaret (1602–1666), was the granddaughter of Edmond Fitzgibbon, 11th White Knight and sister and heiress of Maurice Oge Fitzgibbon, 12th White Knight. She married Sir William Fenton (died 1667). Their children included a son Maurice, created in 1661 a baronet, of Mitchelstown, and a daughter Catherine, who married John King, first Baron Kingston. Through Catherine Mitchelstown Castle passed to the King family, later Earls of Kingston.