For the second creation, it was granted to James FitzGerald, 1st Duke of Leinster, who married to Lady Emily Lennox, the great-granddaughter of King Charles II of the Royal House of Stuart.

In 1554, Thomas's half-brother and only male heir, Gerald FitzGerald, was created Earl of Kildare in the Peerage of Ireland.

After nearly a century as the headquarters of the Royal Dublin Society, which held its famed Spring Show and Horse Show in its grounds, Oireachtas Éireann, the two chamber parliament of the new Irish Free State, rented Leinster House in 1922 to be its temporary parliament house.

Their Carton House seat was sold (though one of Ireland's most historic buildings with perfectly preserved 18th century grounds, it was controversially turned into a hotel and golf course in the late 1990s by the current owner in an act condemned by environmentalists[citation needed]), as later on was their other residence in Waterford.

A controversial claim by claimants who say they are descended from the 5th Duke, which is reported to have been largely debunked by Michael Estorick in 1981, was made in 2006 and subsequently failed.

It was further claimed by Mrs Caudill that a package of documents, witnessed by Edward, Prince of Wales (later Edward VIII), Sir Edgar Vincent, and Lord Feversham, had been lodged by her father with the Crown Office of the House of Lords in 1929, and the family had been denied access to them.

Mrs Caudill believed the documents included evidence that her father agreed to relinquish the title for one generation but made it clear it was to be passed down to his son, her brother Leonard FitzGerald.

[9] The claim was dismissed by Lord Falconer of Thoroton, despite a 30-year campaign by Paul FitzGerald's family reputedly costing £1.3 million.

[10] In 2010, however, DNA evidence was presented that indicates that Paul FitzGerald is related to the wife of the 5th Duke, the former Lady Hermione Duncombe.

The results of the tests found that it was "41 times more probable" that Ms Crawford and Paul FitzGerald were extremely closely related than were from different families.

The proof that Paul FitzGerald is related to the titled family is the first DNA evidence ever produced in the case, and it strongly supports Mrs Fitz-Gerald Caudhill's long-held claim suggesting that her mysterious father was the son of Lady Hermione, the wife of the fifth Duke of Leinster.

The FitzGeralds then adopted a monkey as their crest (and later supporters) and occasionally use the additional motto Non immemor beneficii (Not forgetful of a helping hand).

The word "Abu" or "Aboo", an exclamation of defiance, was the usual termination of the war cries in Ireland, as in a' buaidh, "to victory!