1.  Marriage Index:  Maryland, 1655-1850.  Liahona Research, Orem, UT (Broderbund CD-224):

Cain, Benjamin

Davis, Sarah

3 Oct 1808

Frederick Co.

2.  1810 Census Index and Digital Images (online at Ancestry.com; Image #49 of 106; extracted by Diana Gale Matthiesen):

1810

MD

Frederick Co.

p. 324/550

B Cain

10010-10010-00

These data indicate:

No. ? Sex	Age Class	Therefore Born	Individuals Inferred
1 male	9 or under	1800-1810	= Son A
1 male	26-44	1765-1784	= Benjamin
1 female	9 or under	1800-1810	= Daughter A
1 female	26-44	1765-1784	= Sarah (b. 1783/4)

Two children in two years is pretty fast work.  Were the two children possibly fraternal twins?

3.  1820 Census Index and Digital Images (online at Ancestry.com; Image #4 of 24; extracted by Diana Gale Matthiesen):

1820

MD

Frederick Co.

Election District No. 8

p. 212?

Benjamin Caine

110010-01001-0-100

no slaves

These data indicate:

No. ? Sex	Age Class	Therefore Born	Individuals Inferred
1 male	9 or under	1810-1820	= Son B
1 male	10-15	1804-1810	= Son A
1 male	26-44	1775-1794	= Benjamin
1 female	10-15	1804-1810	= Daughter A
1 female	45 or over	in or bef. 1775	= Sarah (b. 1783/4)
1	person engaged in agriculture

Where are Rebecca and Lydia?  Sarah is in the wrong age class.  Is this really our subject?

4.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):  can't find.

5.  1840 Census Index and Digital Images (online at Ancestry.com; Image #35-36 of 38; extracted by Diana Gale Matthiesen):

1840

MD

Frederick Co.

Election District No. 5

pp. 271B-272A

Benjamin Cain

000 000 010 - 010 000 010

0100000

These data indicate:

No. ? Sex	Age Class	Therefore Born	Individuals Inferred
1 male	50-59	1780-1790	= Benjamin
1 female	5-9	1830-1835	= ?
1 female	50-59	1780-1790	= Sarah (b. 1783/4)
1	person engaged in agriculture

Where are Rebecca and Lydia?  Living next door to Joshua DAVIS, who is also in his 50's, so may be Sarah's brother.

6.  1850 Census Index/Images (online at Ancestry.com; Image #29 of 81):  District of New Market, Frederick Co., MD, p. 252A/499/503, 224/231, enumerated 3 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Sarah Cain	66	F			300	Md
Lydia A "	38	F				Md
Benjamin Syas/Syers	70	M		Carpenter		Md

Living next door to Sarah's daughter, Rebecca, and her husband, Abraham SYAS/SYERS, son of Benjamin SYAS/SYERS.