The secondary sources all seem to have Lucy as William's first wife, but given their marriage date and the fact that Lucy was  his wife in the 1850 Census, Lucy had to have been his second wife.

1a.  Census Index:  U.S. Selected Counties, 1810 (Broderbund CD-313).  Please see my WARNING regarding use of this database (the genders are switched in the numerical data). 

1810

Bobbit, John

KY

Christian Co.

p. 55

10010-2010100

1b.  1790-1870 Census Index (online at Ancestry.com):

1810

BOBBIT

JOHN

KY

Christian Co.

p. 55

20101-10010-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1800-1810	= Stephen (b. 1810) = Willis (b. ca. 1806)
1 male	16-25	1784-1794	= ?
0 males	26-44	1765-1784	= John (b. 1782)
1 male	45 or over	in or bef. 1765	= ?
1 female	9 or under	1800-1810	= Sarah (b. ca. 1808) = Elizabeth (b. ca. 1804)
1 female	26-44	1765-1784	= Esther (b. 1780-90)

The numbers here really don't agree with our subjects' family.  Yet, we know they were here, so who else could it be?

2.  Christian County Genealogical Society (Hopkinsville, KY).  1995.  Christian County, KY, Census Records, 1820-1830-1840.  Simmons Historical Publ., Melber, KY.  (Page number is page in the transcription, not in the census.)  On p.

1820

Bobbett

John

420010 - 11110

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
4 males	9 or under	1810-1820	= William (b. 1818/9) = Emsley (b. ca. 1817) = John Jr. (b. 1813) = Isham (b. 1812)
2 males	10-15	1804-1810	= Stephen (b. 1810) = Willis (b. ca. 1806)
1 male	26-44	1775-1794	= John (b. 1782)
1 female	9 or under	1810-1820	= Lucinda (b. ca. 1811)
1 female	10-15	1804-1810	= Sarah (b. ca. 1808)
1 female	16-25	1794-1804	= Elizabeth (b. ca. 1804)
1 female	26-44	1775-1794	= Esther

3.  Christian County Genealogical Society (Hopkinsville, KY).  1995.  Christian County, KY, Census Records, 1820-1830-1840.  Simmons Historical Publ., Melber, KY.  (Page number is page in the transcription, not in the census.)  On p. 44:

1830

Bobbett

John

002 210 100 - 011 010 100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	10-14	1815-1820	= William (b. 1818/9) = Emsley (b. ca. 1817)
2 males	15-19	1810-1815	= John Jr. (b. 1813) = Isham (b. 1812)
1 male	20-29	1800-1810	= Stephen (b. 1810)
1 male	40-49	1780-1790	= John (b. 1782)
1 female	5-9	1820-1825	= boarder?
1 female	10-14	1815-1820	= boarder?
1 female	20-29	1800-1810	= Elizabeth (b. ca. 1804) or Sarah (b. ca. 1808)
1 female	40-49	1780-1790	= Esther

4.  Christian County Genealogical Society (Hopkinsville, KY).  1995.  Christian County, KY, Census Records, 1820-1830-1840.  Simmons Historical Publ., Melber, KY.  (Page number is page in the transcription, not in the census.)  On p. 76:

1840

Bobbitt

John

101 010 010 - 000 100 010

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= boarder?
1 male	10-14	1825-1830	= boarder?
1 male	20-29	1810-1820	= William (b. 1818/9)
1 male	50-59	1780-1790	= John (b. 1782)
1 female	15-19	1820-1825	= boarder?
1 female	50-59	1780-1790	= Esther

5.  1850 KY Census Index/Microfilm (online at GenealogyLibrary.com) — indexed as "John Bollitt":  Dist. 1, Christian Co., KY, p. 483, 767/824, enumerated 28 Sep 1850 (extracted by Diana Gale Matthiesen — this record extremely difficult to read):

John Bobbitt	67	M	Minister Cal. Bpt Ch.	1000	NC
Lucy Bobbitt	66	F			Va
William Bobbitt	31	M	Minister ? Ch.		Va
Saml H. Allman	16	M			Ky
John M? Allman	13	M			Ky
Zepha ?	12	F			Ky

William was born in Kentucky; this must be census-taker error.
(Zepha's surname is unreadable; she was not indexed.)
Living next door to Isham Bobbitt.

6a.  A.B. Willhite.  [n.d.]  Christian Co., Kentucky, Tax List, 1804-1809.  (self-published; available from author at 4396 Coopertown Rd., Russellville, KY 42276, or from the Christian County Genealogical Society, Hopkinsville, KY):

Pg. in Willhite	Year	Dist.*	Last  Name	First  Name	A	B	C	D	E	Acres	Watercourse
15	1804	North	Bobbitt	John	1	-	-	-	1	200	Tradewater River
46	1805	North	Bobbet	John	[data said to be unreadable]
51	1806	North	Bobbet	John	1	-	-	-	4	150	T W
94	1807	West	Bobbit	John	1	-	-	-	1	200	Tradewater River
-	1808	-	-	-	-	-	-	-	-	-	-
184	1809	West	Bobbet	John	1		-	-	3	200	T W
Legend for numerical data: A = White Males 21 or over; B = White Males 16-20 (this column not used in 1809); C = Blacks over 16; D = Total Blacks; E = Horses
Abbreviations:  T W = Tradewater River
*The county was divided into just two districts:  from 1804 to 1806, into North and South Districts; beginning in 1807, into East and West Districts.

6b.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1810-1813.   (Self-published; available from author at 4396 Coopertown Rd., Russellville, KY 42276, or from the Christian County Genealogical Society, Hopkinsville, KY).

Pg. in Willhite	Year	First  Name	Last  Name	A	B	C	D	E	Acres	Watercourse
-	1810	-	-	-		-	-	-	-	-
54	1811	John	Bobbit	1	-	-	-	4	200	T W
-	1812	-	-	-		-	-	-	-	-
157	1813	John	Bobbet	1		-	-	3	200	T W
Legend for numerical data: A = White Males 21 or over; B = White Males 16-20 (this column used only in 1811); C = Blacks over 16; D = Total Blacks; E = Horses
Abbreviations:  T W = Tradewater River

6c.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1814-1818.   (Self-published.  This book is out of print.  I do not have a copy.  If you have one to sell, please contact me.)

6d.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1819-1823.   (Self-published; available from author at 4396 Coopertown Rd., Russellville, KY 42276, or from the Christian County Genealogical Society, Hopkinsville, KY).

Pg. in Willhite	Year	First  Name	Last  Name	A	B	C	D	Acres	Watercourse
8	1819	John	Bobbitt	1	-	-	5	200	Tradewater River
80	1820	John	Bobbit	1	-	-	5	200	T W
122	1821	John	Bobbett	1	-	-	-	200	-
166	1822	John	Bobbett	1	-	-	4	200	-
209	1823	John	Bobbett	1	-	-	5	200	T W
Legend for numerical data: A = White Males 21 or over; B = Blacks over 16; C = Total Blacks; D = Horses
Abbreviations:  T W = Tradewater River

7.  "John Bobbitt m. Esther Brannon SC > KY," Message #333, by J.A. Powell, in the Bobbitt Family Genealogy Forum at GenForum.  Excerpt:

1) 1804 - Sptbg. Co. Deed Book K; pp. 225-226 24 Oct; John Bobbett (Christian Co., KY) to Reuben Seay... border Thomas Brannon and Reuben Seay... signed John Bobbett and Esther 2) 1832 - Sptbg. Co. Real Estate Settlement File #17 of William Brannon "To Edmond L. Bishop and wife, Thomas Brannon, Dudley Brannon, John Keenum and wife, John Bobbitt and wife, James Brannon, John Brannon, William Brannon, John ? and wife, Samuel Seay and wife, ? Seay, Dudley Seay, and William Seay heirs of Elizabeth Seay ... all heirs and distributees of William Brannon, deceased... real estate of William Brannon, deceased, situated on Lawson fork, bounded by Presley Ballenger, David Golightly and Willamson Seay... This would seem strong proof that John W Bobbitt, Sr. is married 1st to Esther Brannon (sister of my Dudley) not "Hester Boney"...

I agree.

8.  Anon.  1986.  Family Histories:  Christian County, Kentucky, 1797-1986.  Christian County Genealogical Society, Hopkinsville, KY.  Biographical sketch of John W. Bobbitt on p. 79.

9.  Joshua Daniel Bobbitt.  1999.  Family Group Sheet of Isham Drury Bobbitt, Sr. [link died] Citing:
John W. Bobbitt.  1985.  The Bobbitt Family in America.  Washington, DC, pp. 680-684.

10.  Descendants of William Bobbit, 1645-1703 [link died] by Barbara G. Jennings.

11.  LDS.  Family Search: Internet Genealogy Service: IGI - International Genealogical Index and AF - Ancestral File (online at FamilySearch.org).