I've been looking into this George Hay in Annathill, and so far the only primary reference I have found is that sasine in which Elizabeth Hay, wife of Joseph Howie of Meikle Drumgray is described as daughter of George Hay in Annathill (not, be it noted, of Annathill). The sasine is in Volume 12, which covers the period 1709 to 1719, and Elizabeth's marriage was in 1717, so the sasine presumably relates to that.
James Cleland LLD says, in his Annals of Glasgow, that Bishop George Hay (1729-1811) was 'a member of the Annathill family'. He also says that he himself is 'nearly related to the Bishop'. However he does not give any details except that Bishop Hay's father was a Writer to the Signet in Edinburgh. (There is no listing of this James Hay in the List of Members of the Society of Writers to Her Majesty's Signet)
The Dictionary of National Biography says that Bishop Hay was born on 24 August 1729, the only son of James Hay, 'a writer in Dalrymple's office' and Mary Morrison, and grandson of Andrew Hay of Inchnoch. I read somewhere that James Hay's father was George Hay. As Bishop Hay was born in 1729, it is reasonable to suppose that his father James Hay was born around 1700, and hence that his grandfather George was born around 1670.
Andrew Hay of Inchnoch and Gayne was the son of the Reverend John Hay of Ranfield or Renfield and his wife Agnes Forsyth, whose father was David Forsyth of Hallhill, Dykes and Inchnoch. He married Mary Hutcheson and according to Fasti Ecclesiae Scoticanae their second son, another Reverend John Hay, was born in 1654.
James Cleland LLD (1770-1840) was the son of John Cleland of Easter Blairlin and his wife Jean Waddell.
Jean Waddell (1748-1788) was the daughter of James Waddell of Magiscroft and his wife Anna or Anne Howie.
Anna or Anne Howie was born in 1718 at Drumgray, the daughter of Joseph Howie and Elizabeth Hay.
So James Cleland LLD can be shown to be the great-grandson of George Hay of Annathill.
As Elizabeth was married in 1717, it is reasonable to suppose that she was born in about the 1690s, and therefore that George Hay in Annathill, her father, was born in about the 1660s.
So we have George Hay, son of Andrew Hay of Inchnoch, said by Cleland to be of the Annathill family, born around 1670, and George Hay in Annathill, father of Elizabeth, who would have been born in about the 1660s.
Therefore it looks probable that these two George Hays are one and the same, and therefore that James Cleland LLD was first cousin twice removed to Bishop George Hay.
Would anyone care to pick holes in my reasoning, and/or can anyone find a primary source indicating that George Hay, son of Andrew of Inchnoch, is indeed George Hay in Annathill?