Rosa Mary Menpes was the daughter of Rosetta Matilda Venn (d. 1866) and James Grosse. On 27 April 1875 she married Mortimer Luddington Menpes, the painter, etcher and pupil of JW. They had a son, Mortimer James (b. 1879), and two daughters. Their second daughter Dorothy Whistler Menpes, later Mrs Flower, was JW's goddaughter, and she was named in his honour.
The Menpeses met JW in 1880. Rosa Menpes' husband became JW's pupil and studio assistant. They owned several works by JW, including The Blue Band (YMSM 262), Note in Blue and Green (YMSM 307), Study in Brown (YMSM 313), Draped Study (YMSM 320), Portrait of William M. Chase (YMSM 322) and White and Grey: La Cour de l'hôtel, Dieppe (YMSM 325).
JW painted her daughter Dorothy's portrait in 1884/1885, when she was under 2 years of age. She is shown with one bare foot, having pulled off one of her shoes, Note in Flesh Colour and Grey: Portrait of Miss Dorothy Menpes (YMSM 260). JW also painted a watercolour (Master Menpes (M.1017)) and oil (Master Menpes (YMSM 261)) of her son. JW made an etching of the Menpes children about 1887, The Menpes Children (K.261).
From 1888 the Menpes family lived at 25 Cadogan Gardens, their famous lavishly decorated 'Japanese House'. JW and Mortimer Menpes fell out in 1888 over the house, which JW felt copied his ideas and principals. It was auctioned in 1900, and the Menpeses moved to Kent.
Times, London, 25 August 1936, p. 12; Menpes, Mortimer, Whistler as I Knew Him, London, 1904; MacDonald, Margaret F., James McNeill Whistler. Drawings, Pastels and Watercolours. A Catalogue Raisonné, New Haven and London, 1995; Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980; http://genforum.genealogy.com (Venn) (accessed 2005); http://www.familysearch.org (accessed 2005).