Walter De Burgh, 1st Earl of Ulster
De Burgh, Walter, 1st Earl of Ulster, son of preceding, married Maud, daughter and heiress of Hugh de Lacy, Earl of Ulster. At her father's decease, about 1243, he became, in her right, Earl of Ulster.
Sources
52. Burke, Sir Bernard: Dormant, Abeyant, Forfeited, and Extinct Peerages. London, 1866.