The original Barony of Desmond in the province of Munster was held by descendants of Thomas FitzMaurice, Lord OConnello. Thomas was the eldest son of Maurice FitzGerald, Lord of Lanstephan and he was a key supporter of the Lord of Pembroke known as ("Strongbow") in his 1169 invasion of Ireland. Maurice FitzGerald, Lord of Lanstephan was the founder of the FitzMaurice/FitzGerald Dynasty in Ireland. Being descended from the eldest son of Maurice FitzGerald, Lord of Lanstephan, the House of Desmond was a cadet branch of the famous Geraldines; the senior branch, the House of Kildare, were ancestors of the Dukes of Leinster, which was founded by Thomas's brother and 2nd eldest son of Maurice FitzGerald, Lord of Lanstephan namely Gerald FitzMaurice, 1st Lord of Offaly