Judging by the 1910 census, Clyde was really the son of Frank Purvis, but he was raised as a Cox.

1910 census of Kanawha precinct, Fayette Co., West Virginia, enumerated 3 May, lists on p. 17A as household #335, family #349, in the same house as Addie’s parents:
Purvis, Frank, 31, married 2 years, b. Ky Ky Ky; Addie, wife, 21, b. Ky Ky Ky, married 2 years, mother of 1 child, 1 living; Clyde, son, 1, b. WVa Ky Ky.