1850 census of Lincoln Co., Kentucky, district 2, enumerated 24 Aug, lists on p. 76 as family #540:
Alex’r Singleton, 32; Mary, 22; Martha, 4; Nancy, 6/12. All born in Kentucky.

The preceding household is headed by Able Singleton age 55 with wife Ann age 56. The one before that is headed by David Singleton age 22 with wife Mary age 24.

1860 census of Lincoln Co., Kentucky, Stanford P.O., enumerated 29 June, lists on p. 36 as family #225:
Alex’r Singleton, 40, shoemaker; Mary, 33; Martha Ann, 11; Pamelia J., 10; Mary E., 5; Sally A., 3; David C. A., 2; Wm H., 1/12. Thos S. Blankenship, 25, laborer. All born in Kentucky.

Note that Martha Ann is recorded as three years younger than suggested by the 1850 census. If Pamela is really 10 (or even almost 10), then she must the same as the daughter listed as Nancy age 6 months in 1850, but it might be that her age is off by a few years as well.

I cannot find this family in the 1870 census.