This miniature portrait is unsigned. The sitter is idneitfied on notes inside the group frame as Major Stirling.
"Major Stirling, uncle of James Mills of Plas Bellin."
"Major Stirling, uncle of James Wills (2) of Plas Bellin Northop Wales."
It seems that he must have been a brother of the Charlotte Elizabeth Stirling who married Godfrey Wills on 6 Jun 1771.
There was a Major Stirling with the 42nd Highland Regiment, the Black Watch, who acted heroically in Egypt during the Nile Campaign, but it is not known if this is the same Major Stirling. 18d