The Sessions family traveled as far as Fort Kearney with a small, independant company (5 families, 10 wagons). There, for greater security, they attached themselves to the William B. Preston Company. Although, William was not listed in the company roster, information from the introductory paragraph in "Edgar Sessions Autobiographical Sketch," suggests he became a member of the company.
More research is needed to confirm William's date of birth. Date listed reflects family tradition from Family Tree at FamilySearch.org, and data from the 1900 Census.