Looks like John never married per census records. Ellen lived with him.
Sources
"United States Census, 1910," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M57K-NQ9 : accessed 3 December 2016), Ellen Graham in household of John Graham, Hebron, Washington, New York, United States; citing enumeration district (ED) ED 105, sheet 1B, family 13, NARA microfilm publication T624 (Washington D.C.: National Archives and Records Administration, 1982), roll 1088; FHL microfilm 1,375,101.
The Church of Jesus Christ of Latter-day Saints, "Pedigree Resource File," database, FamilySearch (https://familysearch.org/ark:/61903/2:2:S5L2-Q46 : accessed 2016-11-30), entry for John /Graham/.
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DNA Connections
It may be possible to confirm family relationships with John by comparing test results with other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share some percentage of DNA with John: