His sister, Elizabeth Hay, was a noted singer with the Edinburgh Music Society based in St Cecilia's Hall, who married Sir William Forbes, 6th Baronet.

[3] In 1774, Hay was apprenticed in the Edinburgh banking house of his brother-in-law, Sir William Forbes of Pitsligo.

"He became a partner in the firm of Forbes, Hunter and Company in 1782, married into the Scottish aristocracy in 1785, built a house at Kingsmeadows, Peebles and accumulated much property in the burgh.

"[2] Upon the death of his father on 21 October 1810, he succeeded as the 5th Baronet Hay, of Smithfield, county Peebles in the Baronetage of Nova Scotia and was one of the "quiet country gentlemen set" of Edinburgh society.

Together, they lived at Haystoun, Peebles and were the parents of:[4] His wife died on 2 November 1803, before he succeeded to the baronetcy.