— born in CT, presumably in Vernon, Tolland Co., CT:
3.  Frederick H. BRUCE, b. 1831; d. 27 Sep 1883; bur. Elmwood Cem.
4.  Mary Angeline BRUCE, b. 1840/1

1.  Lorraine Cook White, ed.  1994-2000.  The Barbour Collection of Connecticut Town Vital Records: Canterbury Vital Records, 1703-1850.  Genealogical Publ. Co., Baltimore, MD (online at Ancestry.com):

p. 143

BRUCE, Thaddeus, s. Esther COLLINS, single woman, b. Feb. 28, 1793

v. 1

p. 114

2.  1820 Census Index/Images (online at Ancestry.com, Image #2 of 13; extracted by Diana Gale Matthiesen):

1820

CT

New London Co.

Griswold

Roll M33_2

p. 719

Ln. 22

Thadeus C Bruce

000010-11100-0-001

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	26-44	1775-1794	= Thaddeus (b. 1791/2)
1 female	9 or under	1810-1820	= Cathrine (b. 1819/20)
1 female	10-15	1804-1810	= ?
1 female	16-25	1794-1804	= Zilpha (b. 1794/5)
1	person engaged in manufacture

Zilpha is too young to be the mother of the teenage girl.

3.  1830 Census Index/Images (online at Ancestry.com, Image #23 of 78 — indexed "Sadens c Bruse"; extracted by Diana Gale Matthiesen):

1830

RI

Providence Co.

Smithfield

Roll 168

p. 130B

Ln. 26

Thadeus C Bruce

010 001 - 011 101

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1820-1825	= William (b. 1822)
1 male	30-39	1790-1800	= Thaddeus (b. 1791/2)
1 female	5-9	1820-1825	= Mary Angeline (b. 1840/1)
1 female	10-14	1815-1820	= Cathrine (b. 1819/20)
1 female	15-19	1810-1815	= ?
1 female	30-39	1790-1800	= Zilpha (b. 1794/5)

4.  1840 Census Index/Images (online at Ancestry.com, Image #5-6 of 20; extracted by Diana Gale Matthiesen):

1840

CT

Tolland Co.

Vernon

Roll 31

pp. 130B-131A/4151-4152

Ln. 22

Thaddeus Bruce

010 100 100 - 000 110 100

0300000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1830-1835	= Frederick (b. 1831)
1 male	15-19	1820-1825	= William (b. 1822)
1 male	40-49	1790-1800	= Thaddeus (b. 1791/2)
1 female	15-19	1820-1825	= Mary Angeline (b. 1840/1)
1 female	20-29	1810-1820	= Cathrine (b. 1819/20)
1 female	40-49	1790-1800	= Zilpha (b. 1794/5)
3	persons employed in agriculture

5.  1850 Census Every-Name-Index/Images (online at Ancestry.com, Image #4 of 70):  Town of Vernon, Tolland Co., CT, Roll M432_50, 29/31, enumerated 20 Sep 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Thadeus Bruce	57	M		Farmer	2500	Conn
Silpha    "	55	F				Rhode Island
Fred H    "	18	M		Farmer		Conn
Mary A    "	9	F				Conn

6a.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #31 of 96):  Rockville P.O., Vernon, Tolland Co., CT, Roll M653_80, p. 477, PN 31, 219/231, enumerated 11 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Nathen Cox	40	M		Farmer			England
Ann J   "	30	M					"
Arabell "	15	F					Germany
Agnes   "	13	F					Mass
Martin  "	4	M					Conn
Thadeus C Br???	66	M		Farmer	3000	600	"
Zilpha      "	65	F					RI

There's no apparent genealogical connection between the COX's and our subjects.  Listed next to daughter [Mary] Angeline BRUCE (see next source), who is next to son William C. BRUCE.

6b.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #32 of 96):  Rockville P.O., Vernon, Tolland Co., CT, Roll M653_80, p. 478, PN 32, 220/232, enumerated 11 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Angline Bruce

19

F

Conn

Listed between her parents and her brother, William C. BRUCE.  It's actually unlikely that they were in separate domiciles and more likely the enumerator was mis-using the visitation numbers.

7.  Lucius Barnes Barbour.  1929.  "Inscriptions from Gravestones at Vernon, Conn."  New England Historical and Genealogical Record 83(Oct): 496-504.

p. 496	3. Elmwood Cemetery...
p. 497	Cathrine J. daughter of T. C. and Zilpha Bruce, died Oct. 27, 1843, aged 23. Frederick H. Bruce died Sept. 27, 1883, aged 52. T. C. Bruce died Jan. 23, 1869, aged 77.      Zilpha, wife of T. C. Bruce, died July 6, 1868, aged 73...

9.  The Political Graveyard.