Charles James Whistler Hanson was the son of Louisa Fanny Hanson, said to have been a parlourmaid, and JW. On 25 June 1896 Hanson married Sarah Ann Murray.
According to the Pennells, Hanson was adopted by Joanna Hiffernan and went to stay with her at 5 Thistle Grove, despite the fact that JW had been unfaithful to her. JW drew a picture, Charles Hanson (M.587), of his son ca. 1876. Hiffernan continued to look after him as late as 1880 when JW was away in Venice with Maud Franklin, his current mistress.
JW's brother William also acted as Hanson's adviser and supporter. JW himself provided Hanson with money and around 1887 he gave him a vacation job as his secretary. Hanson was at this point studying engineering at King's College, London. When he graduated JW helped him to find a job.
However, their relationship was not close, and he tended to expect too much from his son. JW did not attend his son's wedding in 1896, which unfortunately coincided with Beatrix Whistler's death, nor did he entirely approve, but he sent his best wishes and a cheque.
MacDonald, Margaret F., James McNeill Whistler. Drawings, Pastels and Watercolours. A Catalogue Raisonné, New Haven and London, 1995.