There is a Greene Co TN Gass family in my maternal heritage. However, I don't know to which family line they belong. If I had to wager a guess, I would say a Kinser daughter married into the Gass family. My grandmother's known Greene Co TN lineage is Campbell/Kinser,Campbell/ McMillan and Kinser/Ealy,
At some point in time, the Gass family, of whom I have 2 photos, moved to the Edgar, NE area. It appears the only children born to them were 3 sons, and I don't know the names of the 3 boys or their father. One photo is a family photo, on the front border of the photo it says "Gass Family' and on the back "Aunt Mollie". The other photo show only the 3 sons and appears to have been taken about 5 years after the family photo. On the face of this photo it says "Lena Mae's cousins". "Lena Mae" Lowery is my grandmother. She was born in 1902. Both of the Gass photos were taken at a studio in Edgar, NE. I am not good at recognizing period clothing, but the photos appear to have been taken sometime around 1900.
I don't know if this information will be of any help to you in your search, but it is all I have.