Diane,
I think I found your grandfather and his father on the 1900 US census for Roane County, Tennessee. He could easily be the same person as the profile at https://www.wikitree.com/wiki/Isham-309, but I can't be sure. There seem to have been several people named George Washington Isham -- and possibly it's a name that was handed down for generations.
https://www.familysearch.org/ark:/61903/3:1:S3HT-D18K-3H
Washington Isham, Male, age 34, Married, White, Head, 6 yrs married, born Feb 1866 in Tennessee; Father born Tennessee; Mother born Tennessee
Catherine Isham, Female, age 38, Married, White, Wife, (Had 10 children, 7 still living in 1900. Married for 6 years. Born May 1862 in Tennessee; Father born in Tennessee; Mother born in Tennessee Tennessee 10
(continued below, but I stopped adding extra explanatory words for age, birth date, etc. for the names below -- I just copy/pasted them from FamilySearch. Likely Catherine is not Washington's first wife, since some of the children have been around for longer than Catherine and Washington have been married. The Mcglothlin children may be from Catherine's previous marriage, and Cora may be a daughter from Washington's previous wife, since she's more than 6 years old)
John W Mcglothlin Male 18 Single White Stepson Sep 1882 Tennessee Tennessee Tennessee
James H Mcglothlin Male 14 Single White Stepson Mar 1886 Tennessee Tennessee Tennessee
Thomas J Mcglothlin Male 12 Single White Stepson Feb 1888 Tennessee Tennessee Tennessee
Cora L Isham Female 8 Single White Daughter Jul 1892 Tennessee Tennessee Tennessee
George H Isham Male 4 Single White Son Apr 1896 Tennessee Tennessee Tennessee
Bertie A Isham Female 1 Single White Daughter Aug 1899 Tennessee Tennessee Tennessee
Do any of these names fit with what you already know?
Reba
