The Dunboyne barony came to the Butlers through the marriage in 1320 of Synolda Lady of Dunboyne, only daughter and heiress of Willian le Petyt, 6th Baron of Dunboyne, with Sir Thomas Butler, uncle of the 1st Earl of Ormonde. He had a writ of summons to Parliament as a peer under the style of "Lord of Dunboyne" and took his seat in 1324. Several of his successors were likewise summoned.52

Thomas, b. ca. 1271, had a grant of the Manor of Castle Grace from his brother, knighted before 1314, summoned to Parliament as a peer under title of Lord of Dunboyne, 1324, and and was ancestor of the BARONS DUNBOYNE. He m. 1308, Synolda Le Petit, Lady of Dunboyne and Molyngou.