Raymond Hoover Downer could be your grandfather but Thomas C. Downer can't be your great grandfather.
Raymond H. Downer's parents were Gilbert H. and Josephine Downer.
In 1900 the family was living in Precinct 12, Otero Co., CO.
Gilbert H. Downer, b. WV Oct 1860, marr 8 yrs, bicycle storekeeper shop & repair.
Josephine F., wife, b. OH Oct 1871, she had given birth to six children and all alive in 1900.
Edit B., b. CO March 1893.
Margarett L., b. June 1894, CO.
May Z., b. CO, March 1896, twin.
Raymond H., b. CO, March 1896, twin.
Marion, dau, b. CO Feb 1898.
Alford E., b. CO, Jan 1900, 5/12ths.
In 1910 the Downer family was living in La Junta, Otero Co., CO.
Gilbert Downer, head, b. WV, 49, marr 18 yrs, contractor snow? systems.
Josephine, wife, b. OH, 38.
Edith, b. CO, 18, single.
Lois, b. CO, 15.
Roy [Ray], b. CO, 14.
May, b. CO, 14.
Marion, b. Co. 12.
Alford, b. CO, 10.
Nelson Norton, hired man.
In 1920 some of the family was living in Oakland, Alameda, CA.
Gilbert either died or he and Josephine were divorced after the 1910 but before the 1920 Census.
Josephine F. Downer, head, b. OH, 47, widow, no occupation.
Raymond H., b. CO, 23, single, contractor sewer & drain.
Marian G., dau, b. CO, 21, single.
Alford E., b. CO, 19, single, operator elevator.
Lydia H. Bane, mother, b. OH, 67, widow.
In 1930 Raymond H. Downer and his family were living in San Diego, San Diego, CA.
Raymond H. Downer, b. CO, 34, contractor road-sewer construction.
Verna M., wife, b. IN, 27.
Raymond H., b. AR, 6.
Robert E., b. CA, 4.
Audrey, b. CA, 2.
A Raymond Hoover Downer
Born: 23 March 1896, Lamar, CO
1942 Residence: Berkeley, Alameda, CA
Nearest Relative: Mrs. R. H. Downer, 2212 S. Baldwin, ARcadia, CA.
Source: U. S. World War II Draft Registration Cards 1942.
Raymond H. Downer
Born: 23 March 1896, CO
Died: 6 April 1970, San Joaquin Co., CA
His last residence MIGHT have been Linden.
Source: California Death Index 1940-97.
Sometimes the place of burial is contain in the obituary or in the death certificate. There is an obituary volunteer at geneasearch.com/lookups/ca.htm .
Your great grandparents would have been Gilbert H. and Josephine F. Downer.