Sally -

Thad Barlow was married to Elizabeth S. McDavid 14 Jun 1846 in Baldwin Co, AL. This from Ancestry.com's AL Marriages, 1809-1929 (selected counties) which has him listed as T C Barlow & her as Elizabeth McDavis.

The couple is enumerated 27 Jun 1860 in 263/201 of the 1860 Baldwin Co Census and living with them are Elizabeth's brother, Richmond, William H(?), John, Joel A & AJ.

Census research I've done on this family would make her parents Joel McDavid (found in Baldwin Co in 1840 & in 1840) and an unknown female.

I currently have Elizabeth's siblings as follows (also based on census records - this is a work in progress):
1. William b 1826
2. unknown female b 1820-25
3. unknown female b 1820-25
4. Elizabeth S b 1826 who married T C Barlow
5. Mary b 1831 married James M Steadham 4 Jun 1856 Baldwin County, AL
6. Minerva b 1833
7. Martha b 1835 m A J Steadham 13 Dec 1852 Baldwin Co, AL
8. Andrew J b 1837
9. Richard (Richmond) b 1839
10. William H b 1841
11. John b 1843 [think he married Laura Steadham]
12. Joel A (Frank) b 1845

Hope this helps.