His younger son, Hugh Macmillan, has worked at universities in Swaziland, Zambia and South Africa, and is currently a research associate at the African Studies Centre, University of Oxford. He is the author of "The Lusaka Years: The ANC in Exile in Zambia, 1963–94" (2013); "An African Trading Empire: The story of Susman Brothers & Wulfsohn" (2005), and of "Zion in Africa: The Jews of Zambia" (1999, with Frank Shapiro). He has also written pocket biographies of Chris Hani, Jack Simons and Oliver Tambo and is the co-editor with Shula Marks of "Africa and Empire: W.M. Macmillan, historian and social critic" (1989). His elder daughter, Lindsay, married Alexander Arthur Dow, and had a career as a teacher in Zambia and Scotland. His younger daughter, Catriona, married Colonel Alistair Miller, Queen's Royal Irish Hussars, and had a career as a hotelier in Dorset. She edited, with her mother, "Exiles of Empire", the nineteenth century correspondence of the Pratt family between Scotland, India and Australia.