1a.  Marriage Record:

1b.  F. Edward Wright.  1995.  Early Church Records of Lebanon County Pennsylvania.  Family Line Publ., Westminster, MD (Broderbund CD-166).

St. John's Union Church, Fredericksburg... Elisabeth of Peter Kapp and Christina, b. Dec 10, 1777; bapt. Dec 18, 1777. Spon: Elisabeth Nef.

1c.  Archives of the CUPP-L mailing list (online at RootsWeb.com), specifically, a post by Lynn Cupp:

From "Samuels Lutheran Reformed Baptism Register 1785 - 1867" (Somerset County, PA) compiled by Eber Cockley: Parents                 Child           Born            Christened Peter KUPP & Christina  John Mich.      15 Jan 1790     21 Feb 1790

2.  Census Index:  Colonial America, 1607-1789 (Broderbund CD-310):  not found.

3.  1790 Census Index and Digital Images (online at Ancestry.com; Image #13 of 17; extracted by Diana Gale Matthiesen):¤•

1790

PA

Bedford [now Somerset] Co.

p. 25/253

Ln. 14

Peter Capp

1-3-4-0-0

These data indicate:

Gender and Type	Age Class	Therefore Born	Individuals Inferred
1 free white male	16 or over	in or bef. 1774	= Peter (b. 1750-55)
3 free white males	15 or under	1774-1790	= Son A = Son B = Son C
4 free white females	all ages	in or bef. 1790	= Mother? Mother-in-Law? = Christina = Daughter A = Daughter B

4.  1800 Census Index and Digital Images (online at Ancestry.com; Image #1 of 6; extracted by Diana Gale Matthiesen):¤•

1800

PA

Somerset Co.

Somerset Twp.

p. 127/509

Capp Peter

12101-22002-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	9 or under	1790-1800	= John Michael (b. 1790)
2 males	10-15	1784-1790	= Son C = Son B
1 male	16-25	1774-1784	= Son A
1 male	45 or over	in or bef. 1755	= Peter (b. 1750-55)
2 females	9 or under	1790-1800	= Daughter D = Daughter C
2 females	10-15	1784-1790	= Daughter B = Daughter A
2 females	45 or over	in or bef. 1755	= Christina = Mother? Mother-in-Law?

This enumerator had absolutely exquisite handwriting — it doesn't get any more legible.

5.  1810 Census Index and Digital Images (online at Ancestry.com; Image #1 of 9; extracted by Diana Gale Matthiesen):¤•

1810

PA

Somerset Co.

Somerset Borough

p. 354/374

Ln. 13

Capp Peter

00011-01010-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	26-44	1765-1784	= Son A?
1 male	45 or over	in or bef. 1765	= Peter (b. 1750-55)
1 female	10-15	1794-1800	= Daughter D?
1 female	26-44	1765-1784	= Wife-2 (b. 1770-75)

I guess the children didn't like their step-mother.

6.  1820 Census Index and Digital Images (online at Ancestry.com; Image #1 of 4; extracted by Diana Gale Matthiesen):¤•

1820

PA

Somerset Co.

Somerset Borough

p. 178

Ln. 17

Copp Peter

000001-00001-2-0000

These data indicate (data columns non-standard):

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	45 or over	in or bef. 1775	= Peter (b. 1750-55)
1 female	45 or over	in or bef. 1775	= Wife-2 (b. 1770-75)

7.  1830 Census Index and Digital Images (online at Ancestry.com; Image #21 of 42; extracted by Diana Gale Matthiesen):¤•

1830

PA

Somerset Co.

Somerset Twp.

p. 85

Ln. 16

Peter Capp

001 000 000 100 - 000 100 010 000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	10-14	1815-1820	= ?
1 male	70-79	1750-1760	= Peter (b. 1750-55)
1 female	15-19	1810-1815	= ?
1 female	50-59	1770-1780	= Wife-2 (b. 1770-75)

The teenagers could be grandchildren, other kin, or hired help.