I have to question whether these next three really were children of James and Betsy.  Alex and Isaac are missing in the 1830 and 1840 censuses, and Sarah is missing from the 1840 census.  Were they orphaned children of one of James's brothers?  Did they just move in to help their widowed aunt?  And do we really know that Sarah's maiden name was McWILLIAMS?

.  Alexander "Alex" McWILLIAMS, b. 1821/2, PA
.  Isaac L. McWILLIAMS, b. 1824/5, PA
.  Sarah E. (__?__) BRUENS(?), b. 1831/2, PA

1.  Marriage Record:

2.  1810 Census Index/Images (online at Ancestry.com; Image #4 of 4; extracted by Diana Gale Matthiesen):¤•

1810

PA

Centre Co.

Ferguson Twp.

p. 64/176/255

Ln. 17

James McWilliams

20010-10100-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1800-1810	= Son B = Son A
1 male	26-44	1765-1784	= James
1 female	9 or under	1800-1810	= Catherine or Mary Ann
1 female	16-25	1784-1794	= Elizabeth

3.  1820 Census Index/Images (online at Ancestry.com; Image #2 of 4; extracted by Diana Gale Matthiesen):

1820

PA

Centre Co.

Boggs Twp.

Roll 98 (Book 1), p. 200

Ln. 11

James McWilliams

210010-21010-0-100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1810-1820	= John (b. ca. 1814) = Son C
1 male	10-15	1804-1810	= Son A or B
1 male	26-44	1775-1794	= James
2 females	9 or under	1810-1820	= Eliza (b. ca. 1815) = Mary Ann or Catherine
1 female	10-15	1804-1810	= Catherine or Mary Ann
1 female	26-44	1775-1794	= Elizabeth
1	person engaged in agriculture

4.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315; numerical data courtesy of Kipp Melat):

1830

McWilliams, James

PA

Venango Co.

French Creek Twp.

p. 8

000 210 100 - 001 100 100

These date indicate:

4.  1830 Census Index/Images (online at Ancestry.com; Image #X of X; extracted by Diana Gale Matthiesen):

1830

-

- Co.

- Twp.

p. -

Ln. -

-

-

-

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	15-19	1810-1815	= John (b. ca. 1814) = Son C
1 male	20-29	1800-1810	= Son A or B
1 male	40-49	1780-1790	= James
1 female	10-14	1815-1820	= Eliza (b. 1815) = Catherine or Mary Ann (bef. or aft. Eliza)
1 female	15-19	1810-1815
1 female	40-49	1780-1790	= Elizabeth

Where are Alex and Isaac?

5.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316; numerical data courtesy of Kipp Melat):

1840

McWilliams, James

PA

Venango Co.

Cranberry Twp.

p. 120

000 021 010 - 000 010 010

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	20-29	1810-1820	= John (b. ca. 1814)  = Son C
1 male	30-39	1800-1810	= Son A or B
1 male	50-59	1780-1790	= James
1 female	20-29	1810-1820	= Eliza or Catherine or Mary Ann
1 female	50-59	1780-1790	= Elizabeth

Where are Alex, Isaac, and Sarah?

6.  Census Microfilm Records:  Pennsylvania, 1850 (Broderbund CD-305, Disk 10):  Cranberry Twp., Venango Co., PA, p. 31A, 108/109, enumerated 25 Oct 1850 (extracted by Diana Gale Matthiesen; n.b., there is no date on this page because this enumerator only put the date on the page when the date changed, so all you have to do is leaf back to find the enumeration date, which was on p. 30A):

Betsy McWilliams	55	F	500	Pa
Alex	28	M		"
Isaac	25	"		"
Marion Bruens?	20	M		"
Sarah E Bruens?	18	F		"

Betsy is fibbing about her age by at least five years.  This is the first appearance of Alex, Isaac, and Sarah in James and Betsy's household, so I have to doubt that they are their children.  As for Marion and Sarah, the indexer read their surname as "Bwuous," and Kipp Melat read it as "Brown."  Other sources have it as "Burns" or "Burris."  For certain, it begins with "B" and ends with "s" (not an "n"), but in-between it's really just six bumps — at least Kipp had the number of bumps right, while the indexer clearly got carried away!  I checked every surname in the county beginning with B that could be close, but none was a match.
<time passes>
Could this surname possibly be Kearns?  Elizabeth's sister, Susan, married a John Carner/Carnes, and her sister Mary married a James Karns.

7.  1860 Census.

8.  1870 Census Index/Images (online at Genealogy.com; Image #23 of 24):  Viola P.O., Forest, Richland Co., WI, Roll 1734 (Book 1), p. 628A, PN 23, 164/166, enumerated 1 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Ewing Eliza	54	F	W	Keeping house	3000	845	Pennsylvania
_____ Valentine	26	M	W	Farmer			Pennsylvania
_____ Mary J	24	F	W	Keeping house			Pennsylvania
_____ Martha	23	F	W	At home			Pennsylvania
_____ Sylvester	21	M	W	At home			Pennsylvania
_____ Evaline	17	F	W	At home			Pennsylvania
_____ Horace	14	M	W	At home			Wisconsin
_____ Franklin	12	M	W	At home			Wisconsin
_____ Nathaniel	28	M	W	Farmer			Pennsylvania
_____ Wm S	2	M	W				Wisconsin
McWilliams Elisabeth	84	F	W	Staying			Pennsylvania