Here is the WWI Draft Registration for Charlie Sebert Walton. On it, he says he is responsible for a brother who is dependent on him. That would usually be a boy under age 12. Also, he is working with Tom Walton - you can investigate that relationship.
"United States World War I Draft Registration Cards, 1917-1918," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K6ZM-YPK : accessed 27 April 2016), Charlie Sebert Walton, 1917-1918; citing Grayson County, Virginia, United States, NARA microfilm publication M1509 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,984,717.
Happy hunting! -NGP