John Forbes-Sempill was born 21 August 1863 to William Forbes-Sempill, 17th Lord Sempill (1836-1905) and Frances Emily Abercromby (1835-1887) and died 28 February 1934 of unspecified causes. He married Gwendolen Emily Mary Prodgers (1869-1944) 22 June 1892 .
Children
| Name | Birth | Death | Joined with |
| William Francis Forbes-Sempill, 19th Lord Sempill (1893-1965) | |||
| Gwendolen Janet Forbes-Sempill (1897-1910) | |||
| Margaret Forbes-Sempill (1905-1966) | |||
| Ewan Forbes of Craigievar, Bt (1912-1991) | 6 September 1912 Scotland, United Kingdom | 12 September 1991 | Isabella Mitchell (c1913-2002) |
Siblings
Residences
Footnotes (including sources)
| ‡ General |