Did you know that Richard was part Irish? It's past St. Paddy's day but worthy of discussion. Richard Duke of York was the son of Anne Mortimer. Her father Roger Mortimer, 4th Earl of March was the eldest son of Philippa Plantagenet daughter of Lionel, Duke of Clarence and Elizabeth de Burgh, 4th Countess of Ulster. She was born at Carrickfergus Castle near Belfast. She was a descendent of William de Burgh and his wife, the daughter of the King of Thomond, Domnall Mór mac Toirrdelbach Ua Briain (Donald the Great, O'Brien) who himself was a descendent of Brian Boru.