"ADAIR, Robert - Surgeon General HM Forces (Robin Adair) died 1790. Seeking parentage of his reputed daughter, Sophia Adair Howard, born 1774."
would have a copy of Robert Adair's will wherein it mentions Sophia.
His will was proved in the Prerogative Court of Canterbury, England,according to an index edited by Anthony J. Camp for a Society of Genealogists 1976 London publication. The entry shows - "1790 ADAIR, Robert, Esq., Surgeon Gen of H.M. Forces, (Administration with Will attached) Middx Apr 169."
Vicar's Index to the Prerogative Wills of Ireland shows a "copy" in 1791.