John and Joseph are said to be twins.

1.  Marriage Record:

2.  1830 Census Index/Images (online at Ancestry.com, Image #19 of 24; extracted by Diana Gale Matthiesen):¤

1830

PA

Mifflin [now Juniata] Co.

Greenwood [now Susquehanna] Twp.

Roll 147

p. 406

Ln. 15

Philip Coup

010 020 - 001 110 100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	5-9	1820-1825	= sibling? son? step-son?
2 males	20-29	1800-1810	= sibling? = Philip (b. 1806)
1 female	10-14	1815-1820	= sibling? step-daughter?
1 female	15-19	1810-1815	= sibling?
1 female	20-29	1800-1810	= Molly (b. 1800)
1 female	40-49	1780-1790	= mother? mother-in-law? sibling?

Where's Elizabeth?  Is this really our subject's household?  Obviously, we have more than just a nuclear family in the household, and it's difficult to know just who the members are.  Philip is old enough to be the father of the youngest boy, but none of the others, who are most likely either his or Molly's siblings.  The middle aged woman could be old enough to be Philip's mother, but only just old enough to be Molly's mother.  She could just as easily be an older sibling of either.  Molly is old enough to be the mother of both the youngest boy and the youngest girl, which may mean the latter came with her from a previous marriage.

3.  1840 Census Index and Digital Images (online at Ancestry.com; Image #3-4 of 16; indexed as "Cap. Philip" — note the period, instead of a comma, which affects your ability to search on the name because you can only pull it up by searching on the surname alone; extracted by Diana Gale Matthiesen):¤•

1840

PA

Juniata Co.

Greenwood [now Susquehanna] Twp.

pp. 218B-219A

Ln. 3

Philip Cup

020 011 000 - 301 000 100

0200000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	5-9	1830-1835	= Jacob (b. 1831/2) = Joseph (b. 1830/1) = John (b. 1830/1)
1 male	20-29	1810-1820	= ?
1 male	30-39	1800-1810	= Philip (b. 1806)
3 females	4 or under	1835-1840	= Sarah (b. 1837/8) = Lucy (b. 1834/5) = Eliza (b. 1833/4)
1 female	10-14	1825-1830	= Elizabeth (b. 1830)
1 female	40-49	1790-1800	= Mary (b. 1799/1800)
2	persons engaged in agriculture

We should have three males born between 1830 and 1835; Lucy and Eliza are in the wrong age class.

4.  1850 Census Index/Images (online at Ancestry.com; Image #21 of 44):  Greenwood [now Susquehanna] Twp., Juniata Co., PA, p. 342/623, 2040/2070, enumerated 4 Nov 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

Phillip Roop	44	M		Laborer	200	Penna
Mary Roop	40	F				"
John Ropp	19	M		Laborer		"
Joseph Roop	19	M		"		"
Jacob Roop	18	M		"		"
Eliza Roop	16	F				"
Lucey Roop	15	F				"
Sarah Roop	12	F				"

It really is "Roop," not even "Koop."  Mary should be 50.  Listed next to Michael & Eva (GLACE) STRAUB. 

5.  1860 Census Images (online at Ancestry.com; Image #328 of 430):  Mahontongo P.O., Susquehanna Twp., Juniata Co., PA, p. 796, PN 236, 1632/2, enumerated 2 Aug 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

Philip Cupp	53	m		Laborer	400	250	Pennsylvania
Molly Cupp	60	f					"
Elizabeth Stroap	31	f		widow		150	"
Philip	8	m					"
Henry	6	m					"

Elizabeth is their divorced/deserted daughter; Philip and Henry are Elizabeth's children.  Listed next to Michael & Eve (GLACE) STRAUB/STROUP. 

6.  1870 Census Images (online at Ancestry.com; Image #17 of 23):  Mohontongo P.O., Susquehanna Twp., Juniata Co., PA, Roll 1353 (Book 1), p. 370A, PN 17, 115/120, enumerated 15 Aug 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤•

Cupp Philip	62	M	W	Farmer	800	200	Pa
____ Cathrane	70	F	W				"
____ Lusy	21	F	W	Teacher			"

Lucy should be age 35.  Listed next to Philip STROUP. 

7.  1880 Census Images (online at Ancestry.com; Image #8 of 30):  Dimmsville (Village), [Greenwood Twp.,] Juniata Co., PA, p. 356D, PN 8, SD 7, ED 134, enumerated 5 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	11	13	14	21	23	24	25	26
60	65	Cupp Jacob	W	M	47			/		Blacksmith				PA	PA	PA
		[Jacob's wife and children]
		____ Philip	W	M	75	Father			/	Retired Laborer	12			PA	(Germany)	PA

The fact that "Germany" is in parenthesis suggests Philip has some uncertainty as to his father being born in Germany.  There were several RHOADS and HUPP families in the neighborhood.

8.  WorldConnect (online at RootsWeb.com), where a file cites the next source.

9.  Georgeann B. Whelan.  1976.  The Cupp Family.  Self-published, Ellicott City, MD.  [not seen]