Joseph married Gertrude Lydia Castle on 19 Jan 1895 in St. Bartholomew the Great, Smithfield, London, England. Gertrude was born on 3 Dec 1874 in Hertford, Hertfordshire, England; died on 28 Jul 1955 in Eltham, Kent, England; was buried on 2 Aug 1955 in Eltham Cemetery, Eltham, Kent, England. [Group Sheet]

1. Marjorie Joan Slater was born on 30 Apr 1906 in Ware, Hertfordshire, England; died after 1939.
2. Muriel Violet Slater was born on 15 Jul 1895 in Enfield, Middlesex, England; was christened on 22 Jul 1896 in St. Mark's, Enfield, Middlesex, England; died after 1911.