1850 Census: District 12, Maury Co., TN lists:

Chandler, John 37, born in TN
Chandler, Susan 35, born in TN
Chandler, Caroline 10, born in TN
Chandler, Nancy 8, born in TN
Cosby, Nancy 62, born in VA

Can anyone help me with this family?
Who were John's parents?
Where were the couple in the 1840 census?
Is Nancy Cosby the mother of Susan Chandler?
What became of this family?
HELP! HELP! HELP!