The WWI Registration card disagrees with the birth date but has the same spouse listed and VIrginia birthplace. Possible mistake or intentional difference? Reference here: 
↑ "United States World War I Draft Registration Cards, 1917-1918," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K6C1-Y1L : 12 December 2014), Thomas Seymour, 1917-1918; citing Fairfax County, Virginia, United States, NARA microfilm publication M1509 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,984,712.
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VRYR-FLJ : accessed 12 August 2017), Thos Seymour in household of Violet Williamson, Mount Vernon Magisterial District, Fairfax, Virginia, United States; citing enumeration district (ED) 30-18, sheet 2A, line 10, family 19, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 4261.