The youngest son of George Leslie D.D. (Rector of Clones & Kilmore) and Margaret Montgomery (sister of Colonel Alexander Montgomery (1686–1729) of Convoy House, County Donegal and Ballyconnell House, County Cavan) and first cousin of James Leslie, Bishop of Limerick, Ardfert and Aghadoe.
The youngest offspring of George Leslie D.D. (Rector of Clones & Kilmore) and Margaret Montgomery (sister of Colonel Alexander Montgomery (1686–1729) of Convoy House, County Donegal and Ballyconnell House, County Cavan), and first cousin of James Leslie, Bishop of Limerick, Ardfert and Aghadoe.