Given the difference in age between George and Keziah, we would expect that he had an earlier wife, and the 1820 census supports that his wife, then, was older than Keziah.  Also, given Keziah's age, we wouldn't expect her to have birthed a child as early as 1810.

Most secondary sources (at WorldConnect) give these parents for Keziah:
Father:  James SPURGEON (1756-1810)
Mother:  Elizabeth FARMER

But one secondary source (at GenForum) gives these parents:
Father:  Frederick SPURGEON
Mother:  Thirza McGREW

1.  Marriage Record:

2.  1810 Census Index/Images (online at Ancestry.com):  not found, but given that none of George's children were born before 1810, it appears George had not married by 1810.  His father, William BENSON, is living in Monongalia [now Preston] Co., VA [now WV] (p. 484).

3.  1820 Census Index/Images (online at Ancestry.com; Image #2 of 15; extracted by Diana Gale Matthiesen):

1820

VA [now WV]

Preston Co.

p. 845

Ln. 4

Benson George

200010-30010-0-100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1810-1820	= William = James (b. 1810)
1 male	26-44	1775-1794	= George (b. 1780)
3 females	9 or under	1810-1820	= Catharine (b. 1819/20) = Elizabeth (b. 1813) = Daughter A
1 female	26-44	1775-1794	= Wife-1
1	person engaged in agriculture

List was roughly alphabetized.

4.  1830 Census Index/Images (online at Ancestry.com; Image #3 of 66; extracted by Diana Gale Matthiesen):

1830

VA [now WV]

Preston Co.

p. 2A

Ln. 7

Benson George

010 200 100 - 211 101

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1820-1825	= John (b. 1822/3)
2 males	15-19	1810-1815	= William = James (b. 1810)
1 male	40-49	1780-1790	= George (b. 1780)
2 females	4 or under	1825-1830	= Celia (b. 1827/8) = Maria (b. 1825/6)
1 female	5-9	1820-1825	= Polly (b. 1820-25)
1 female	10-14	1815-1820	= Catharine (b. 1819/20)
1 female	15-19	1810-1815	= Elizabeth (b. 1813)
1 female	30-39	1790-1800	= Keziah (b. 1796/7)

List was roughly alphabetized.

5.  1840 Census Index/Images (online at Ancestry.com; Image #49 of 69 — mis-indexed "Georeg Benson"; extracted by Diana Gale Matthiesen):

1840

VA [now WV]

Preston Co.

p. 231A

Ln. 16

George Benson

010 120 010 - 002 010 100

0300000

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1830-1835	= Joseph (b. 1830/1)
1 male	15-19	1820-1825	= John (b. 1822/3)
2 males	20-29	1810-1820	= James (b. 1810) = William
1 male	50-59	1780-1790	= George (b. 1780)
2 females	10-14	1825-1830	= Celia (b. 1827/8) = Maria (b. 1825/6)
1 female	20-29	1810-1820	= Catharine (b. 1819/20)
1 female	40-49	1790-1800	= Keziah (b. 1796/7)
3	persons employed in agriculture

6.  1850 Census Index/Images (online at Ancestry.com; Image #136 of 278):  District No. 45, Preston Co., VA [now WV], p. B, 1377/1377, enumerated 1 Nov 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

George Benson	70	M		Farmer	80	Md
Kesiah    "	53	F				Va
Catharine "	30	F				"
John      "	27	M				"
Celia     "	22	F				"
Joseph    "	19	M		Labourer		"

Listed two households from son, James BENSON.

7.  1860 Census Index/Images (online at Genealogy.com; Image #1 of 1):  Post Office at Guseman's Store, Brandonvile [near Bruceton Mills], District No. 2, Preston Co., VA [now WV], Roll 1372 (Book 1), p. 74, 491/483, enumerated 11 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Kesiah Benson	70	F					Va
John      "	30	M		Farmer	400	183	"
Joseph    "	24	M		Farmer	400	183	"
Cecilia   "	26	F					"
Marcellus "	6	M					"
Allen     "	4	M					"

The ages in this census do not jibe with the ages in other censuses — who was the informant, Marcellus?!  The only one with an incentive to fib about their age was Cecilia.  The fact that John and Joseph have equal amounts of property suggests that they just came into an inheritance, which jibes with the fact that their father died in 1859.  Marcellus and Allen are almost certainly Keziah's grandchildren.

8.  1870 Census Index/Images (online at Genealogy.com, Image #16 of 40):  Rowlesburg P.O., Pleasant Twp., Preston Co., WV, Roll 1697 (Book 1), p. 140B, PN 16, 106/106, enumerated 30 Sep 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Benson Joseph ?	37	M	W	Farmer	700	300	Virginia
______ Caseah	75	F	W	Keeping House			Virginia
______ William A	16	M	W	Farm Laborer			Virginia

I can't read Joseph's middle initial.  "Caseah" (Keziah) is Joseph's mother.  William is presumably one of Keziah's grandchildren.  Living next to Joseph's brother, James BENSON. 

9.  LDS.  Family Search: Census Records: 1880 United States (online at FamilySearch.org):  not found.

10.  Messages in the Benson Family Genealogy Forum (online at GenForum.com).

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