He was the fourth son of
George Hay, 8th Earl of Kinnoull by his wife Abigail, second daughter of
Robert Harley, 1st Earl of Oxford. In 1752 he married Mary, daughter of Peter Flower, a London merchant. In that year he was appointed
consul at Cadiz, then in 1754 was consul-general in Portugal. He became envoy extraordinary to Portugal in 1757 and minister plenipotentiary in 1762. In 1772 he was appointed
Governor of Barbados. His wife died on 11 October 1775, and on 24 January 1779 Hay was remarried in Barbados to Mary Harbourne Barnwell, but he died later that year on 21 October. ==References==