He may be a brother of the John S. McClain who married Sibby Reeves in 1855 in Fleming Co. (Conjecture based on the daughter named Sibby, and on the migration of this family to Fleming Co.)

Bath Co., Ky marriage records list the marriage on 12 July 1847 of James McClain and Nancy Shropshire.

1850 census of Bath Co., Ky, division 2, lists as family #497:
James McLain, 24, farmer; Nancy, 24; Ellen M., 2; Thomas Bradshaw, 25. All born in Kentucky.

1860 census of Bath Co., Ky, Owingsville P.O., enumerated 30 July, lists on p. 154 as family #1101:
James McClane, 30, farmer; Nancy, 30; Sarah, 11; Susan, 9; Rebecca, 6; John, 2.

The ages for the children recorded here (other than Susan) are so inconsistent with birth records that one wonders if the household was really visited, or just recorded from the memory of the census taker.

1870 census of Fleming Co., Ky, Flemingsburg precinct, enumerated 24 June, lists on p. 31 as family #187/188:
McClain, James, 44, laborer; Emily, 32; Susan, 21; Sally A., 19; Emily, 17; John, 14; Cibby, 11; Alfred, 2; McCarty, Jackson, 22, laborer.

The age gap between Cibby and Alfred suggest that only Alfred is Emily’s daughter. The birth order for Susan and Sarah (Sally) has been switched. Emily should be only 14 and John only 11, from their birth records.

Jackson McCarty would later marry Susan McClain.