If Peter & Adaline were married in 1857/8 or even in 1855/6, then Peter had a prior wife who was the mother of George W.  Either that or George's age in the 1860 census is wrong, which is certainly possible.

1.  Marriage Record:

2.  1850 Census Index/Images (online at Ancestry.com; Image #2116 of 204):  Germantown, Philadelphia Co., PA, Roll M432_824, p. 246A, enumerated 6 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

180	204	Samuel Stroup	25	M		Manufacturer		Penna
		Joanna    "	23	F				"
		Louisa    "	4	F				"
		John      "	1	M				"
		Susan Schaeffer	22	F				"
	205	John F. Swain	35	M		Shoe Maker		Maryland
		Sarah     "	44	F				Penna
		Peter Stroup	16	M		Shoe Maker		"

This is the only Peter STROUP (or variation) I can find in Philadelphia County who comes close to being our subject.  His occupation also supports his identity.  Samuel STROUP is presumably Peter's brother. 

3.  1860 Census Every-Name Index and Images (online at Ancestry.com, Image #182 of 815):  Philadelphia P.O., Philadelphia (Ward 15), Philadelphia Co., PA, Roll M653_1165, p. 182, PN 182, 1183/1123, enumerated 11 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

Peter Loucey	68	M		Carpenter			Italy
Maria   "	69	F					Pennsylvania
Kate    "	33	F					"
Adaline Stroup	25	F					"
Peter     "	24	M		Shoe Maker			"
Geo W     "	6	M					"
Samuel    "	10/12	M					"
Emanul Street	11	M					"
Thos?     "	7	M					"

Adaline and Peter STROUP should both be 27 years old.  Peter & Maria LOUCEY/CLUSEY are Adaline's parents. 

4.  1870 Census Index/Images (online at Genealogy.com, Image #134 of 142):  Summer Road Falls P.O., Philadelphia (Ward 28, District 92), Philadelphia Co., PA, Roll 1445 (Book 1), p. 334B, PN 134, 859/867, enumerated 14 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤•

Kephard Chas	24	M	W	Laborer		700	Penna
"    Lena	23	F	"	Keeping house			Wurtemberg
"    Lena	3?	F	"				Penna
Stroupe Peter	50	M	"	Laborer		150	Penna
"    Adeline	45	F	"				Penna
"    Peter	10	M	"				Penna
"    Adeline	8	F	"				Penna
"    Saml	5	M	"				Penna
"    Caroline	3	F	"				Penna
White? Margaret	30	F	"	Domestic Servant			Penna
Quinn John	30	M	"	Gardener			Penna
Shehan Conrad	25	M	"	"			Penna
"   John	23	M	"	"			Penna

Peter & Adeline should both be 37 years old.

5.  1880 Census (indexed at FamilySearch.org; page image online at Ancestry.com, Image #19 of 44):  Norwood Ave., Philadelphia (Ward 28, 18th Division), Philadelphia Co., PA, Roll T9-1187 (Book 1), p. 509C, PN 19, SD _, ED 603, enumerated 9 Jun 1880, official enumeration date 1 Jun 1880 (extracted by Diana Gale Matthiesen):¤•

1880:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).

1

2

3

4

5

6

8

9

10

13

19

20

21

24

25

26

154

159

Stroup Peter

W

M

47

/

Shoemaker

/

/

PA

PA

PA

______ Adeline

W

F

47

Wife

/

House Keeper

PA

PA

PA

______ Anna

W

F

13

Dau

/

PA

PA

PA

______ Thomas

W

M

9

Son

/

at School

/

PA

PA

PA

______ Catharine

W

F

7

Dau

/

at School

/

PA

PA

PA

6.  1890 Census:  the 1890 Census Population Schedules were destroyed.

7.  1900 Census Index/Images (online at Genealogy.com, Image #366 of 469):  5 Hopkins Court, Philadelphia, Philadelphia Co., PA, Roll 1463 (Book 2), p. 261B, SN 8, SD 1, ED 487, enumerated 15 Jun 1900, official enumeration date 1 Jun 1900 (extracted by Diana Gale Matthiesen):¤•

1900:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
		1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	19	20	22	23	24	25	27
*	5	152	160	Stroutz Peter	Head	W	M	Aug 1832	67	M	44			PA	PA	PA	Shoemaker	0	Y	Y	Y	R	H
				_______ Adeline	Wife	W	F	Nov 1832	67	M	44	8	3	PA	PA	PA			Y	Y	Y
				Clusey Harry	Boarder	W	M	May 1852	48	S				PA	PA	PA			Y	Y	N
	*Hopkins Court

If they were married in 1856/7, then Peter had a prior wife who was the mother of George W. STROUP.

8.  1910 Census Index/Images (online at Genealogy.com, Image #458 of 564):  2 Tulls Court, Philadelphia City (Ward 22), Philadelphia Co., PA, Roll 1396 (Book 1), p. 231B, SN 11B, SD 1, ED 440, enumerated 20 Apr 1910, official enumeration date 15 Apr 1910 (extracted by Diana Gale Matthiesen):¤•

1910:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
		1	2	3	4	5	6	7	8	9	10	11	12	13	14	17	18	19	20	21	22	23	24	25	26	28	30
*	2	225	230	Stroup Peter	Head	M	W	78	M1	52			PA	US	PA	Eng	None	pensioned				N	N		R	H	UA
				______ Adaline	Wife	F	W	75	M1	52	8	3	PA	US	PA	Eng	housework	out	W	N	0	Y	Y
				Clusay Harry	Nephew	M	W	52	S				PA	PA	PA	Eng	housework	private family	W	N	0	Y	Y	Y
*Tulls Court

Peter & Adaline should both be 77 years old.  As best I can figure, they haven't been married 52 years, but rather were married in 1852.  If they really were married in 1857/8, then Peter had a prior wife who was the mother of his son, George W. STROUP.

9.  1920 Census Index/Images (online at Ancestry.com, Image #22 of 28):  5835 Crittenden St., Germantown, Philadelphia City (Ward 22), Philadelphia Co., PA, Roll T625_1623 (Book 2), p. 11B, SN 11B, SD 1, ED 572, enumerated 13/14 Jan 1920, official enumeration date 1 Jan 1920 (extracted by Diana Gale Matthiesen):¤•

1920:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).

1

2

3

4

5

6

7

9

10

11

12

16

17

18

19

21

23

25

26

27

28

*

5835

223

226

Steiner George W

Head

R

M

W

62

M

Y

Y

PA

PA

PA

Y

????

Automobiles

W

_______ Catharine

Wife

F

W

46

M

Y

Y

PA

PA

PA

Y

None

W

[George & Catharine's children et al.]

Stroup Adeline

Mother in law

F

W

88

W

Y

Y

PA

PA

PA

Y

None

*Crittenden St.

10.  Civil War Pension Index (index and images online at Ancestry.com):

Name of Soldier	Stroup, Peter
Name of Dependent	Widow	Stroup, Adaline
	Minor
Service	K 17, B 21?, D 98 Pa Inf.
Date of Filing	Claim	Application No.	Certificate No.	State from which Filed
1890 Aug 1	Invalid	879702	608522	Pa
1911 Apr 13	Widow	962722	723857	Pa
	Minor

11.  Anon.  1999.  Compiled Civil War Military Service Records from the United States National Archives.  Ancestry, Inc., Provo, UT (online at Ancestry.com):

Surname	Given Name	Company	Unit	Rank - Induction	Rank - Discharge	Allegiance	Notes
Stroup	Peter	K	17 Pennsylvania Infantry	Private	Private	Union
Stroup	Peter	D	98 Pennsylvania Inf.	Private	Sergeant	Union
Straub	Peter	D	98 Pennsylvania Inf.	Private	Sergeant	Union	Stroup Peter

12a.  Anon.  1997-2000.  Military Records of Individual Civil War Soldiers.  Historical Data Systems, Provo, UT (online at Ancestry.com):

Name:	Peter Stroup
Enlistment Date:	25 April 1861
Distinguished Service:	Distinguished Service
Side Served:	Union
State Served:	Pennsylvania
Unit Numbers:	2175 2175
Service Record:	Enlisted as a Private on 25 April 1861. Enlisted in Company K, 17th Infantry Regiment Pennsylvania on 25 April 1861. Mustered out Company K, 17th Infantry Regiment Pennsylvania on 02 August 1861 in Philadelphia, PA.

12b.  Anon.  1997-2000.  Military Records of Individual Civil War Soldiers.  Historical Data Systems, Provo, UT (online at Ancestry.com):

Name:	Peter Stroupp
Enlistment Date:	29 Aug 1861
Distinguished Service:	Distinguished Service
Side Served:	Union
State Served:	Pennsylvania
Unit Numbers:	2371 2371
Service Record:	Enlisted as a Private on 29 August 1861. Enlisted in Company D, 98th Infantry Regiment Pennsylvania on 29 August 1861. Promoted to Full Corporal on 01 May 1865. Promoted to Full Sergeant on 13 June 1865. Mustered out Company D, 98th Infantry Regiment Pennsylvania on 29 June 1865 in Washington, DC.

13.  Philadelphia National Cemetery, Philadelphia, Philadelphia County, Pennsylvania (online at interment.net):

Stroupp, Peter, d. 04/01/1911, SGT CO D 98th PA INF, Plot: 1, *

*Records with an asterisk at the end indicates (sic) those that have not been verified as accurate by the U.S. Department of Veterans' Affairs.

14.  Messages posted to the STROUP Surname Board (online at Ancestry.com).