I cannot find this family in the 1900 or 1910 censuses, not even doing first name only searches. (There are also a lot of Jones, Riddle and Perkins families that I can’t find in 1910 who should be in Rowan Co., judging by the reported birthplaces and marriages of their children around that time. Considering the many intermarriages between these families, I suspect that either some census pages were lost or some area wasn’t visited.)

1920 census of Rowan Co., Ky, precinct #9 (Wagoner), enumerated 2 Jan, lists on p. 1A as family #4/5:
Grigory, John, 50; Mary, wife, 40; Carmia, 21, dau; Dora, 17, dau; Elmer, 12, son; Hattie, 9, dau; Clella, 5 2/12, son; Linda, 2 4/12, dau.

1930 census of Rowan Co., Ky, Morehead precinct, enumerated 21 April, lists on p. 8B as family #143:
Gregory, John, 58, age at first marriage 26, farmer; Mary E., wife, 50, age at first marriage 18; Clella, son, 15; Linda, dau, 12; Lester, son, 9; Blankenship, Susan, mother, 68, widowed, age at first marriage 16. All born Ky Ky Ky.

The relationship for Susan Blankenship should be mother-in-law. The next household is headed by their daughter Dora and her husband Jesse Johnson.