— born in Venango Co., PA:
3.  (Daughter A) STROUP, b. 1820-25
4.  John STROUP, b. 1820/1
5.  Daniel S. STROUP, b. 1824/5
6.  (Son B) STROUP, b. 1825-30
7.  Lydia F. STROUP, b. 1830-35 
8.  Elizabeth STROUP, b. 1822/3 
9.  Casper J. STROUP, b. 1835/6

1.  Marriage Record:

2.  1820 Census Index/Images (online at Ancestry.com; Image #4 of 4; extracted by Diana Gale Matthiesen):¤•

1820

PA

Venango Co.

Richland Twp.

Roll M33_114

p. 14A

Ln. 14

Peter Stroup

200010-00100-0-___

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1810-1820	= Henry (b. 1817/8) = Son A
1 male	26-44	1775-1794	= Peter (b. 1792)
1 female	16-25	1794-1804	= Sarah (b. 1795/6)

3.  1830 Census Index/Images (online at Ancestry.com; Image #9 of 10; extracted by Diana Gale Matthiesen):¤•

1830

PA

Venango Co.

Rockland Twp.

Roll M19_164

p. 62

Ln. 7

Stroup Peter

211 001 - 010 001

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	4 or under	1825-1830	= Son B = Daniel (b. 1824/5)
1 male	5-9	1820-1825	= John (b. 1820/1)
1 male	10-14	1815-1820	= Henry (b. 1817/8)
1 male	30-39	1790-1800	= Peter (b. 1792)
1 female	5-9	1820-1825	= Daughter A
1 female	30-39	1790-1800	= Sarah (b. 1795/6)

4.  1840 Census Index/Images (online at Ancestry.com, Image #3-4 of 14; extracted by Diana Gale Matthiesen):¤•

1840

PA

Venango Co.

Rockland Twp.

Roll M704_497

pp. 108B-109A

Ln. 3

Peter Stroup

101 210 010 - 020 100 100

0100000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= Casper (b. 1835/6)
1 male	10-14	1825-1830	= Son C
2 males	15-19	1820-1825	= Daniel (b. 1824/5) = John (b. 1820/1)
1 male	20-29	1810-1820	= Henry (b. 1817/8)
1 male	50-59	1780-1790	= Peter (b. 1792)
2 females	5-9	1830-1835	= Elizabeth (b. 1822/3) = Daughter B
1 female	15-19	1820-1825	= Daughter A
1 female	40-49	1790-1800	= Sarah (b. 1795/6)
1	person employed in agriculture

5.  1850 Census Index/Images (online at Ancestry.com; Image #13 of 36):  Venango Twp., Butler Co., PA, Roll 432_760, p. 348B, 669/675, enumerated 4 Sep 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

Sarah Stroup	54	F				Pa
Elizabeth "	17	F				Pa
Margaret  "	26	F				Pa
Sarah J   "	6	F				Pa
Mary E    "	5	F				Pa
Peter P   "	4	M				Pa
Robert L  "	2	M				Pa
Andrew    "	1	M				Pa
William Logue	20	M		Collier		Pa

The big question here is whether Margaret (LOGUE) STROUP is a widow or is just not living with her husband because, if she's a widow, then Sarah's son, Henry R. STROUP, was Margaret's second husband.  The fact that Peter & Sarah had an older son (older than Henry) who does not appear in the 1850 census, suggests that Margaret may, indeed, be the elder son's widow.  It is not at all unusual for a bachelor son to step in and marry his brother's widow.  If only Butler County had marriage records!  William LOGUE is presumably Margaret's brother. 

5b.  1850 Census Index/Images (online at Ancestry.com; Image #11 of 36):  Venango Twp., Butler Co., PA, p. 347B, 654/660, enumerated 4 Sep 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

Henry Stroup	32	M		Collier		Pa
John     "	29	M		Do		Pa
Casper J "	14	M				Pa

6.  1860 Census Index/Images (online at Ancestry.com, Image #423 of 649):  Lineville P.O., Pinegrove Twp, Venango Co., PA, Roll M653_1189, p. 421, PN 144, 950/950, enumerated 12 Aug 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

C H Reed	35	M		Shoemaker	120	100	Germany
Elizabeth "	28	F					Pa
Mary J    "	21	F					"
Sarah Stroup	60	F		widow			"
George Mealy	73	M		widower			"

Reed should be HOLDENREED.

7.  Rockland Township Cemeteries (online at the Venango County PAGenWeb site):

Rockland... Peter Stroup, 1792 - 8 May 1850

It is clear from the form of these records that these are not verbatim tombstone readings, but compilations based on tombstones and other unknown sources — so caveat emptor!