Asa B. Crosthwaite was the son of Aaron Crosthwait and Eleanor “Nelly” Brockman of Clark Co., Ky. His father is listed as a son, and he is listed as a grandson, in the 1807 will of his grandfather, Jacob Crosthwait (whose wife was also a Brockman.) Additional information about the Crosthwait settlers of Clark Co. can be found in various local histories.

Asa B. Crosthwait purchased land in Lawrence Co., Alabama four times between 1833 and 1849, and married his second wife Eliza Madeline Miller (6 Jan 1819 - 17 Jun 1845) in Decatur, Morgan Co., Alabama on 13 April 1837

Records are ambiguous as to whether the children of Asa B. Crosthwait and Mary Wilson were born in Clark Co., Ky or Lawrence Co., Alabama. He owned land in both places. The earliest land transactions in Alabama seem to be in 1833, and Mary died in Clark Co. in 1836, but in the 1850 census, his children Aaron (born 1823), Ellen (born 1825) and Catherine (born 1835) all listed their place of birth as Alabama.

Most probably Aaron and Ellen were really born in Kentucky.