"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M9BH-N7K : accessed 12 October 2017), Guy F Smith in household of Willard W Smith, Winchendon Town (east & north part), Worcester, Massachusetts, United States; citing enumeration district (ED) 1707, sheet 4B, family 93, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,695.
Thank you to Kitty Smith for creating WikiTree profile Smith-45630
It may be possible to confirm family relationships with Guy by comparing test results with other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree: