His elder sister, Lady Augusta Hay (the first wife George Boyle, 4th Earl of Glasgow), succeeded to the Etal estate in 1806.
From his father's first marriage to Rebecca Lockhart, he had one half-sibling, Lady Mary Hay, who married Gen. John Scott of Balcomie.
[2][3] In 1798, he succeeded to the earldom of Erroll following the death of his elder brother George, who died without issue.
[2] From 1817 to 1819, he was Lord High Commissioner to the General Assembly of the Church of Scotland.
They were the parents of three children, the last of which was born after his death:[2][6] Lord Erroll died on 26 January 1819 and was succeeded by his eldest surviving son, William.