Secondary sources do not agree on the identity of Sterling's parents.

Some secondary sources contend the genders on this marriage were reversed, that this individual is a male Eli HURT and a female Starling WILLIS, which begs the question as to the identity of James M. WILLIS's mother. 

1.  Jordan R. Dodd, ed.  1993.  Kentucky Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-229):

Willis, Starling	Hurt, Ely	9 Nov 1825	Todd Co.
Willis, Starling	Simons, Malinda	3 Oct 1827	Todd Co.
Willis, Sterling	Rager, Martha	5 Apr 1833	Todd Co.

2.  1830 Census Index/Images (online at Ancestry.com):  not found, and I did a page-by-page search of the county.  Presumably, Sterling is a widower living with kin (i.e., not the head-of-household).  The only Sterling WILLIS in Todd Co., KY, was the senior one who married Sarah PAYNE.

3.  1840 Census Index/Images (online at Ancestry.com, Image #60 of 65 — list was roughly alphabetized; extracted by Diana Gale Matthiesen):

1840

KY

Todd Co.

Roll 124

pp. 272

Ln. 19

Willis Starling

002 001 - 210 001

0200000

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	10-14	1825-1830	= Henry (b. 1827/8) = James (b. 1825/6)
1 male	30-39	1800-1810	= Sterling (b. 1803/4)
2 females	4 or under	1835-1840	= Elvira (b. 1837/8) = Mariah (b. 1835/6)
1 female	5-9	1830-1835	= Mary (b. 1833/4)
1 female	30-39	1800-1810	= Martha (b. 1809/10)
1	person employed in agriculture

4.  1850 Census Every-Name-Index/Images (online at Ancestry.com, Image #7 of 100):  District No. 1, Todd Co., KY, Roll M432_219, p. 199A, 50/51, enumerated 23 Jul 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Sterling Willis	46	M		Farmer		Ky
Martha	25	F				"
Mary	16	F				"
Maria	14	F				"
Elvira	12	F				"
Elizabeth	8	F				"
Sarah	5	F				"
David	7	M				"
Martha	4	F				"
John	2	M				"
Hulda	10/12	F				"
James M Willis	24	M				"

Listed next to John RAGER (æ 32, b. KY).

5.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #112-113 of 169):  Elkton P.O., Todd Co., KY, Roll M653_396, pp. 782-783, PN 112-113, 795/795, enumerated 8 Aug 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Martha Willis	50	F				50	Ky
Mary Willis	25	F					Ky
Mariah Willis	23	F					Ky
Elvira	20	F					Ky
E	18	F					Ky
Ed	17	M		F			Ky
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S E	15	F					Ky
M A	13	F					Ky
John	12	M					Ky

Listed next to Martha's stepson, J.M. WILLIS (æ 33, b. KY); and, in the other direction, listed five households from Martha's brother, J.F. [John Ferguson] RAGER (æ 50, b. KY). 

6.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).