In "The Hamilton Manuscripts" published by Sir James Hamilton in Belfast in 1867, it is recorded that William Hamilton, brother of "Captain James Hamilton of Newcastle, who was slain in His Majesty's service against the Irish rebels near Benburb on the fifth day of June, 1646," married as his second of three wives a daughter of Brian MacHugh Aghorley Magennis, who was the mother of his two sons, James and Jocelyn, and also of his two daughters.

Most likely a Magennis to the core, Jocelyn was killed in 1690 in a duel which he fought with Bernard Ward, then Sheriff for the County of Down. The dispute arose in the grand jury room, and they immediately went out and fought close to the Abbey of Down, where they were both killed in the ensuing duel. A letter relating to the matter is still in existence and is (or was) in the possession of the Earl of Roden, at Tollymore Park, which reads as follows: