His father died when he was only seven years old and he was placed in the guardianship of his grandmother, the dowager Lady Drogheda, who petitioned the Crown to restore to him all lands forfeited by the family during the political troubles of the 1640s and 50s.
Lord Longford (as he then was) died at Fleming Hall, Anticur, in 1726 and was buried in the MacDonnell family vault in Bonamargy Friary at Ballycastle, the burial place of the Earls of Antrim.
He left only one child, a daughter, Helen Fleming, who lived and died in Paris on 7 August 1748.
He left as his sole heiress his daughter who married Felix O’Connor of County Donegal.
Following her husband's death, she sold Fleming Hall and moved to Craigs, Finvoy, and then to America.