1.  Jordan R. Dodd, ed.  1993.  Kentucky/ Virginia Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-229):

Holeman, Jacob	Dunkerson, Phebe	10 Feb 1805	Rockingham Co., VA
Underwood, William	Holeman, Ann	8 Feb 1822	Christian Co., KY
Underwood, Nathan	Holeman, Adelaide C.	21 Mar 1827	Christian Co., KY
Underwood, Van	Holman, Mary	23 Dec 1830	Christian Co., KY
Myrtle, William C.	Holman, Elizabeth	13 Nov 1835	Christian Co., KY

Is this our Elizabeth?

2a.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):

1840

Underwood, Nathan

KY

Christian Co.

Hopkinsville

p. 188

2b.  Christian County Genealogical Society (Hopkinsville, KY).  1995.  Christian County, KY, Census Records, 1820-1830-1840.  Simmons Historical Publ., Melber, KY.  On p. 57 (of the book, not the census):

1840

Underwood

Nathan

101 000 100 - 002 101 010

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= Robert (b. 1837/8)
1 male	10-14	1825-1830	=
1 male	40-49	1790-1800	=
2 females	10-14	1825-1830	= Sarah (b. 1831/2) =
1 female	15-19	1820-1825	=
1 female	30-39	1800-1810	= Adelaide
1 female	50-59	1780-1790	= Phoebe (b. 1784/5)

Either Sarah was tallied in the wrong category or her age is wrong in the 1850 Census.

3.  1850 Census Index/Microfilm (online at GenealogyLibrary.com):  District No. 2, Christian Co., KY, p. 381A, enumerated 4 Sep 1850 (extracted by Diana Gale Matthiesen):

315	340	Phebe Holeman	55	F		1200	Virginia
	341	Adelaide Underwood	38	F		1200	"
		Sarah Underwood	18	F			Kentucky
		Robert L  "	12	M			"

Like many a widow, Adelaide has shaved a couple of years off her age.

4.  Broderbund.  World Family Trees.  Vol. 22, Pedigree #977.