William was born in 1862. Possibly died before 1910, he is not in the census with his wife, but she lists herself as married once.
Year: 1900; Census Place: Pittsburgh Ward 11, Allegheny, Pennsylvania
11 Devillier Street
William S Horner head, 38/m, Apr 1862, md 17yrs, PA/PA/PA, teamster
Odessa Horner wife, 36/f, Feb 1864, md 17yrs, 8births/4living, PA/PA/PA
Eva B Horner dau, 14/f, Sep 1885, OH/PA/PA, school
Elizabeth M Horner dau, 12/f, Jun 1887, PA/PA/PA, school
William S Horner son, 8/m, Jul 1891, PA/PA/PA, school
Elsie W Horner dau, 6/f, Aug 1893, PA/PA/PA
↑ Year: 1900; Census Place: Pittsburgh Ward 11, Allegheny, Pennsylvania; Page: 7; Enumeration District: 0144; FHL microfilm: 1241359; Original data: United States of America, Bureau of the Census. Twelfth Census of the United States, 1900. Washington, D.C.: National Archives and Records Administration, 1900. T623, 1854 rolls.