On 31 December 1864, in Moscow, Dumas married Nadjeschda von Knorring (1826 – April 1895), daughter of Johan Reinhold von Knorring and widow of Alexander, Prince Naryschkine. The couple had two daughters: Marie-Alexandrine-Henriette Dumas, born 20 November 1860, who married Maurice Lippmann and was the mother of Serge Napoléon Lippmann (1886–1975) and Auguste Alexandre Lippmann (1881–1960); and Jeanine Dumas (3 May 1867–?), who married Ernest d' Hauterive (1864–1957), son of George Lecourt d' Hauterive and his wife Léontine de Leusse.