Percy Thomas, the son of Serjeant Ralph Thomas, was a painter and etcher. His brother Ralph was a law partner of JW's solicitor J. A. Rose. His other brother Edmund was a dealer and print publisher at 39 Old Bond Street in London.
In 1874 Percy etched Arrangement in Grey: Portrait of the Painter (YMSM 122) for the frontispiece of the first catalogue of JW's etchings, published by his brother Ralph. In 1873 Ralph had bought The Forge (K.68) for £3.10.0 (#10628). In 1874 JW asked Ralph to supply him with two small plates for his new etching, possibly Reading a book (K.111), Tatting (K.112) or The Muff (K.113), prepared by Percy or the printer Auguste Delâtre (#10892). In 1887 Edmund held an exhibition of The Works of James Whistler, Etchings and Drypoints in his Bond Street gallery (#00172).
Thomas, Ralph, A Catalogue of the Etchings and Dry-points of James Abbott MacNeil [sic] Whistler, London and New York, 1874; Bénézit, E., Dictionnaire des Peintres, Sculpteurs, Dessinateurs et Graveurs, 8 vols, Paris, 1956-61; Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980; Maas, Jeremy, The Victorian Art World in Photographs, London, 1984; .