— born in Cape Girardeau Co., Missouri Territory [now MO]:
  2.  Sarah HILL, b. 12 Nov 1812
  3.  James B. HILL, b. 27 Sep 1814
  4.  William HILL, b. 3 Jan 1817
  5.  Dorcas HILL, b. 20 Dec 1818
  6.  Simeon E. J. HILL, b. 1820/1, not 25 Jun 1828
  7.  Martha Caroline HILL, b. 12 Jan 1821

— born in Cape Girardeau Twp., Cape Girardeau Co., MO:
  8.  Thomas Green HILL, b. 7 Mar 1823
  9.  Hannah Matilda HILL, b. 3 Mar 1826

10.  Ezekiel B. R. HILL, b. 31 Aug 1830
11.  Joel R. HILL, b. 31 Mar 1833

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

Ezekiel HILL Death: 14 Jan 1847 Marriage: May 1810, Cape Girardeau, Missouri Spouse: Rachel BLOUNT Death: 03 Dec 1846 Source: patron submission

Children, all born in Jackson, Cape Girardeau, Missouri Mary HILL; Birth: 02 Feb 1811 Sarah HILL; Birth: 12 Nov 1812 James HILL; Birth: 27 Sep 1814 William HILL; Birth: 03 Jan 1817 Darcus HILL; Birth: 20 Dec 1818 Martha C. HILL; Birth: 12 Jan 1821 Thomas G. HILL; Birth: 07 Mar 1823 Hannah M. HILL; Birth: 03 Mar 1826 Simeon E. J. HILL; Birth: 25 Jun 1828 Ezekiel B. R. HILL; Birth: 31 Aug 1830 Joel R. HILL; Birth: 31 Mar 1833 Father: Ezekiel HILL; Mother: Rachel BLOUNT Source: patron submission

The 1850 census show Simeon as age 29 (i.e., born in 1820 or 1821), so if his birthday is Jun 25th, then he was born in 1820.  All it would take is the mis-reading of one digit (or a single typo) to change 1820 to 1828, and that's what appears to have happened.

2.  1810 Census:  Missouri Territory was not formed until 1812; no census available.

3.  1820 Census:  Missouri Territory did not become a state until 1821; no census available.

4.  1830 Census Index/Images (online at Ancestry.com, Image #33-34 of 76; extracted by Diana Gale Matthiesen):

1830

MO

Cape Girardeau Co.

Roll 72

p. 445

Ln. 5

Ezekiel Hill

111 110 100 - 111 201

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1825-1830	= Simeon (b. 1828)
1 male	5-9	1820-1825	= Thomas (b. 1823)
1 male	10-14	1815-1820	= William (b. 1817)
1 male	15-19	1810-1815	= James (b. 1814)
1 male	20-29	1800-1810	= ?
1 male	40-49	1780-1790	= Ezekiel (b. 1790)
1 female	4 or under	1825-1830	= Hannah (b. 1826)
1 female	5-9	1820-1825	= Martha (b. 1821)
1 female	10-14	1815-1820	= Dorcas (b. 1818)
2 females	15-19	1810-1815	= Sarah (b. 1812) = Mary (b. 1811)
1 female	30-39	1790-1800	= Rachael (b. 1790)

Listed 17 lines above "Emry B. M. Hill" (æ 15-20 with wife æ 15-20).  Also in the county:  John HILL (æ 20-30), Thomas HILL (æ 30-40), and Margaret HILL (æ 30-40, widow w/4 children).

5.  1840 Census Index/Images (online at Ancestry.com, Image #3-4 of 16; extracted by Diana Gale Matthiesen):

1840

MO

Cape Girardeau Co.

Cape Girardeau Twp.

Roll 221

pp. 256B-257A

Ln. 11

Ezekeal Hill

012 210 010 - 001 100 100

0501000

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1830-1835	= Joel (b. 1833)
2 males	10-14	1825-1830	= Ezekiel (b. 1830) = Simeon (b. 1828)
2 males	15-19	1820-1825	= Thomas (b. 1823) = ?
1 male	20-29	1810-1820	= James (b. 1814)
1 male	50-59	1780-1790	= Ezekiel (b. 1790)
1 female	10-14	1825-1830	= Hannah (b. 1826)
1 female	15-19	1820-1825	= Martha (b. 1821)
1 female	40-49	1790-1800	= Rachael (b. 1790)
1	person employed in agriculture

6a.  1850 Census Every-Name-Index/Images (online at Ancestry.com):  Ezekiel & Rachel are deceased.  All the children are accounted for, except I can't find daugheter, Hannah Matilda (HILL) BELL, or son, Ezekiel B. R. HILL. 

6b.  1850 Census Every-Name-Index/Images (online at Ancestry.com, Image #33 of 292):  District 14, Cape Girardeau Co., MO, Roll M432_394, p. 357A, 217/226, enumerated 15 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Hezekiah Hall	41	M		Carpenter		NC
M A       "	39	F				Mo
James E   "	17	M		"		"
S E J     "	29	M		"		"
Joel R Hill	17	M		"		"
M A     "	7	F				"

M.A. HALL is our subject's married daughter, Mary Ann (HILL) HALL.  S.E.J. "HALL" should be surnamed HILL because he's our subject's widowed son, Simeon E. J. HILL, and the child, M.A. HILL, is presumably his daughter. Joel R. HILL is also our subject's son.

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