This represents the husband of Nancy Sexton. If he was about the same age as his wife, then he would fit in the birth order as a son of Charles McClain and Comfort Sexton, but if so, it would be further evidence that Nancy is a granddaughter of John Sexton and Elizabeth Ingram rather than their daughter.

The 1850 census of Morgan Co., Ky, lists with the family of John and Elizabeth Sexton:
Nancy McClain, 28; Melvina, 6; Mary, 1.

Nancy is very likely to be a granddaughter of John Sexton and Elizabeth Ingram, rather than their daughter, because Elizabeth would have been about 52 when Nancy was born. (She might instead be a niece, but living with one’s grandparents is much more common than living with an aunt and uncle.)

The marriage date is estimated from the age of Melvina in the 1850 census. It could be as early as 1837, if some earlier children died young. There is no marriage record for this couple in Morgan Co., but the earliest McClain marriage in that county is 1846, so the McClains probably did not migrate into Morgan until the mid-forties. I should check Montgomery and Bath counties.