Secondary sources disagree as to the parentage of our subject, and I have found no documentation proving their identity.  Based on the evidence and deductions given below, I think the most likely father of our subject is Abraham CORBIN of Clermont Co., OH, son of Nathan CORBIN (Sr.) & Sarah JAMES of Harford Co., MD.

There can hardly be any doubt that Sarah CORBIN, wife of Miles MATTOX, is our subject's sister because 1) they were both born in Ohio within two years of each other; and 2), more importantly, they are living next door to one another in the 1840 census of Lake Co., IN, where they are the only CORBINs in the county.  As Sarah was married in 1832 in Clermont Co., OH, it is a reasonably safe assumption that James and Sarah were both born in Clermont Co., OH.  Note that Miles MATTOX's father, Elijah MATTOX, was in the 1820 census of Clermont Co., OH.

My research shows that all CORBINs in Clermont Co., OH, at least through the 1880 census, are descendants of one couple:  Nathan CORBIN & Sarah JAMES of Harford Co., MD.  About 1815, Widow Sarah (JAMES) CORBIN and her children came to Clermont Co., OH.  In the 1820 census of Clermont Co., we find listed as head-of-household:  widow Sarah,  her son John CORBIN (h/o Mary PEDDICORD), her son Nathan CORBIN, Jr. (h/o Sophia ENLOWS), her son Abraham CORBIN (wife's name unknown), and her grandson Nicholas CORBIN (s/o John & Mary, h/o Nancy Ann ENLOWS).

Many secondary sources have Nathan CORBIN, Jr., as the son of John CORBIN, Sr., presumably because both Nathan Jr. and John's son, Nicholas, appear to have married sisters (Sophia and Nancy Ann ENLOWS — but were they aunt and niece?).  In any case, John (b. 1760) is too young to be the father of Nathan Jr. (b. 1776).  These birthyears are from both tombstones and the censuses, so are not mere estimates.  John Sr. and Nathan Jr. are almost certainly brothers, not father and son.

James, our subject, was born in 1813 and his sister, Sarah, in 1811; therefore, we would expect to find them living with their parents in the 1820 census and to be tallied in the youngest age class (under 10).  If we check the CORBIN households in the 1820 census of Clermont Co., OH, we find only three with at least one male and one female in the under 10 age class:  Nathan CORBIN, Jr. & Sophia ENLOWS, Nicholas CORBIN & Nancy Ann ENLOWS, and Abraham CORBIN. 

Nathan CORBIN, Jr. & Sophia ENLOWS
This couple is the one most often given as our subject's parents.  The problem with this couple is that their son, James CORBIN (b. 1817/8), married Rebecca BARKLEY, and their daughter, Sarah CORBIN (b. 1803), married William BAINUM. 

unfinished...

— born in West Liberty, Putnam Co., MO:
6.  James Polk CORBIN, b. 13 Jul 1850; d. 31 Oct 1916, Unionville, Putnam Co., MO
7.  George Washington CORBIN, b. 16 May 1853; d. 1926, Wichita, Sedgwick Co., KS
8.  Martha Jane CORBIN, b. 27 May 1856; d. 7 Mar 1916, Ayr, Adams Co., NE
9.  Nancy Ann CORBIN, b. 2 Feb 1860; d. 26 Sep 1950, Hastings, Adams Co., NE

1a.  Database to an Index of Indiana Marriages through 1850.  Indiana State Library, Genealogy Division, Indianapolis, IN [link died].

Last Name	First Name	Last Name, Spouse	First Name, Spouse	County	Date	Remarks
Corwin	James	Casteel	Cynthia	LaPorte	2-5-1837
Cowan	James	Casteel	Cynthia	LaPorte	2-5-1837

1b.  Jordan R. Dodd, ed.  1993.  Missouri Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-227):  not found.

1c.  LDS.  Family Search: Internet Genealogy Service:  IGI - International Genealogical Index (online at FamilySearch.org).

James CORBIN Birth: 15 May 1813, Clermont, Ohio; Death: 18 Jan 1891, Ayr, Adams, Nebraska Father: Nathan CORBIN; Mother: Sophia ENLOW Marriage: 02 May 1837, La Porte, Indiana Spouse: Cynthia Ann CASTEEL;  Birth: 10 Aug 1819, Michigan City, LaPorte, Indiana; Death: 18 Jan 1903, Ayr, Adams, Nebraska Father: William Henry CASTEEL; Mother: Mary Source: patron submission

Names plus birth and death dates and places of the children are also from this source.

2.  1840 Census Index/Images (online at Ancestry.com; Image #13-14 of 18; extracted by Diana Gale Matthiesen):

1840

IN

Lake Co.

pp. 94B-95A/184-185

Ln. 28

James Corbin

100 010 - 000 010

0100000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= William (b. 1838)
1 male	20-29	1810-1820	= James (b. 1813)
1 female	20-29	1810-1820	= Cynthia (b. 1819)
1	person employed in agriculture

Listed next to James's sister, Sarah (CORBIN) MATTOX.

3.  1850 Census Index/Images (online at Ancestry.com; Image #2-3 of 9 — mis-indexed "Carbin"):  District No. 29, Dodge & Putnam Cos., MO, pp. 3A-#B, 252/254, enumerated 17 Oct 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

James Corbin	34	M		Farmer		Ohio
Syntha    "	30	F				dito
Wm        "	12	M				Indiana
Nathaniel "	9	M				dito
Mary E    "	6	F				dito
[next page]
Sary C Corbin	4	F				Indiana

Someone had penciled out "Putnam" and added "Dodge" in pencil, but the ink original was "Dodge & Putnam."

4.  1860

5.  1870 Census Images (online at Ancestry.com; Image #7 of 20):  Unionville P.O., Jackson Twp., Putnam Co., MO, Roll 801, Book 1, p. 258A, PN 7, 45/45, enumerated 19 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Corbin James	56	M	W	Farmer	1000	800	Ohio
______ Cynthia	50	F	W	Keeps house			Do
______ James R	20	M	W	at home			Missouri
______ Geo W	17	M	W	Do			Do
______ Martha J	14	F	W	Do			Do
______ Nancy A	9	F	W	Do			Do
O??g Mary H	9	F	W	Do			Virginia
Brown Martha	39	F	W	Keeps house			Indiana
_____ James G???	8	M	W	at home			Arkansas

Living next door to Emily CORBIN, widow of their late son, William T. CORBIN.

6.  LDS.  Family Search: Census Records: 1880 United States (online at FamilySearch.org):

Census Place: District 62, Ayr, Adams, Nebraska
Source: FHL Film #1254743; NARA Film #T9-0743; Pg 93B
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
James CORBIN	Self	M	M	W	66	OH	Farmer	--	PA
Cynthia CORBIN	Wife	F	M	W	61	OH	Keeping House	PA	PA
James P. CORBIN	Son	M	S	W	29	MO	Farmer	MO	MO