Lydia Webb was both John’s wife and his stepsister, but John’s father did not marry Cynthia Fairchild Webb until about 1874, at which time John would have been about 27, so it wouldn’t have been like they grew up together.

1880 census of Elliott Co., Ky, Moccasin precinct, lists as part of household #117, with his father and stepmother:
John, son, 35, b. Va/Va/Va; Liddy, 18, dau in law, b. Ky/Ky/Ky; Rhoda E., 11/12, granddau, b. June, Ky/Ky/Ky.

1900 census of Elliott Co., Ky, Moccasin precinct, enumerated 18 June, lists on p. 8A as family #115/117:
Kegley, John, farmer, 55, b. May 1845, Ky/Va/Va; Lydia, wife, 38, b. Feb 1862, Ky/Ky/Ky, married 21 years, mother of 9 children, 9 living; Noah, son, 18, b. Sep 1881; Amanda R., dau, 16, b. Dec 1883; Cynthia A., dau, 14, b. Apr 1886; Jincy S., dau, 11, b. Mary 1889; Lousina, dau, 9, b. Oct 1891; Benjamin C., son, 6, b. May 1894; Vesta May, dau, 4, b. May 1896; Hattie M., dau, 1, b. Jan 1899; Benjamin F., brother-in-law, 25, b. Nov 1874, Ky/Va/Ky. All children born Ky/Ky/Ky.

Benjamin was both John’s half-brother and Lydia’s half-brother. John’s parents were Henry Kegley and Ann Moyer, Lydia’s parents were Henry Webb and Cynthia Fairchild, and Benjamin’s parents were Henry Kegley and Cynthia Fairchild.

1910 census of Elliott Co., Ky, Moccasin precinct, enumerated 28 April, lists on p. 7A as family #106:
Kegley, Benjamin F, 35, b. Ky Va Va, single, farmer; Lydia, sister, 48, b. Ky Va Va, widowed, mother of 10 children, 10 living; Benjerman C., nephew, 15; Vesta, neice, 13; Myrtle, neice, 10; Lela, neice, 7. All children born Ky Ky Ky. (The misspelling of niece is the enumerator’s error, not mine.)