William Michael Rossetti was the second son, third child, of the Italian Dante scholar and political refugee Gabriele Pasquale Giuseppe Rossetti and the half-Italian Frances Mary Lavinia Polidori. He had three siblings: Maria Francesca (b. 1827), Dante Gabriel (b. 1828) and Christina Georgina (b. 1830). In 1874 he married Lucy Madox Brown, the daughter of the painter Ford Madox Brown. She was also a painter.
W. M. Rossetti was an art critic, biographer and bibliographer. He worked as a clerk for the Inland Revenue from 1845, although he had wanted to be a doctor and had shown an interest in art and literature from a young age. He continued to write and draw in his spare time and attended evening classes at the Life School with his brother. In 1857 he joined Ruskin's class at the Working Men's College. He was one of the founder members of the Pre-Raphaelite Brotherhood, and became the group's secretary and chronicler. It was he who edited The Germ and composed its opening sonnet and preface.
Rossetti contributed regular articles on art to the The Spectator from 1850 to 1858, Fraser's Magazine from 1861 to 1865 and The Academy from 1873 to 1878, and published such art critical works as Fine Art: Chiefly Contemporary (1869). He was one of the earliest champions of Whistler and in 1867 resigned from the Burlington Fine Arts Club along with D. G. Rossetti in protest at Whistler's expulsion. He appeared on his behalf during the Ruskin trial of 1878.
In 1889 he wrote a volume on D. G. Rossetti's painting and poetry, and followed this in 1895 with a biography of his brother. In 1901 he translated his father's versified autobiography. He also edited a number of editions of Christina's poetry including a complete edition in 1903.
W. M. Rossetti wrote introductions for a number of important literary works, including a new edition of Shelley's works, commissioned by Moxon and published in 1869. Since his youth he had been attracted to Shelley and founded the Shelley Society with Dowden and Garnett in 1886. He was also responsible for introducing the works of Walt Whitman, with whom he was a correspondent, to the British public, editing an edition of his poetical works in 1860. In his lifetime Rossetti was in contact with some of the most significant figures of Victorian history, as is evidenced by his memoir Some Reminiscences.
Rossetti, W. M., Dante Gabriel Rossetti as Designer and Writer, London, 1889; Rossetti, W. M., Dante Gabriel Rossetti: His Family Letters with a Memoir, 2 vols, London, 1895; Rossetti, W. M., Ruskin: Rossetti: Pre-Raphaelitism, London, 1899; Rossetti, W. M., Pre-Raphaelite Diaries and Letters, London, 1900; Rossetti, W. M., Rossetti Papers 1862-1870, London, 1903; Rossetti, W. M., Some Reminiscences, 2 vols, London, 1906; Bornand, Odette (ed.), The Diary of W.M. Rossetti 1870-1873, Oxford, 1977; Fredeman, William E. (ed.), The PRB Journal, Oxford, 1975; Maas, Jeremy, The Victorian Art World in Photographs, London, 1984; Peattie, R. W. (ed.), Selected Letters of W. M. Rossetti, University Park, PA, 1990.