1830 census of Bath Co., Ky, lists on p. 219, line 10:
William Sexton, 1 male 20-29, 1 female 20-29, 1 female under 5.

This suggests a birthdate of 1801 to 1810 for both William and Nancy.

1840 census of Morgan Co., Ky, lists on p. 306a, line 12 (between Elija Tolliver and John Sexton):
William Sexton, 1 male 30-39; 1 female 30-39; 1 male under 5, 1 male 5-9; 2 females under 5, 2 females 5-9, 1 female 10-14.

The female 10-14 is likely the same one who was under 5 in 1830. The male 5-9 would be Benjamin. There should be two males under 5, John and Presley. This census also shows 4 daughters born between 1830 and 1840, of which I've only identified two (and even that involves a tentative assignment for Rhoda.)

Six children born between 1830 and 1840 suggests that there may be a pair of twins.

(In 1830 John Sexton immediately followed Elija Tolliver, indicating that sometime between 1830 and 1840 William Sexton most likely bought part of John Sexton's land.)

I cannot find this family in 1850. (Which is a shame, since it would help to identify the unknown daughters, as well as resolve some of the age discrepancies.)

1860 census of Bath Co., Ky, Owingsville P.O., enumerated 13 Aug, lists on p. 232 as family #1683 (next door to Benjamin Sexton age 26):
William Sexton, 45, Va; Nancy, 43, Ky; Mary, 24; John, 23; Presley, 22; William, 18; Martin, 17; Prudence, 15; Obediah, 12; Nancy, 5. All children born in Ky.

Due to the difference between the birthdate of about 1801-1810 implied by the 1830 and 1840 census, and the birthdate of about 1815 implied by the 1860 census, I originally thought the 1860 census record could not be the same William Sexton who married Nancy Davis in 1828. But the discovery of the death record for Prudence (Sexton) Muncie, which lists her parents as William Sexton and Nancy Davis, suggests that the 1860 census reading is in fact for the same William Sexton who married Nancy Davis. His age is probably reported about 5 years too young here.

Whether the wife Nancy here in 1860 is the same one as Nancy Davis is more questionable, since women don’t have children as old as men do.

There are rather large age discrepancies between this census and later ones on many of the children as well. For example, Martin, who is listed here as 17, gives his age in most later censuses consistent with a birthdate in 1840, which would make him 20 in 1860.

1870 census of Menifee Co., Ky, Frenchburg precinct, enumerated 27 July, lists on p. 13 as family #98/94:
Sexton, William, 60, farmer; Elizabeth, 45; Frances (f), 8; Rebecca, 3; Lafayette, 1. All born in Kentucky.