A few references have been found to Brocks in Overton, Fentress, and Pickett Counties.

In 1813, Joel Brock signed a petition to raise a military unit.  Click here to view the transcription.

A Brock family outline at Tribal Pages contains the following local references:

Brock, George Ambrose, Born Mar 09 1789 in Knox Co. Tennessee, Died Apr 12 1841 in Fentress Co. Tennessee

Brock, Mary, Born 1791 in Knox Co. Tennessee, Died Dec 19 1855 in Red Hill, Fentress Co. Tennessee

Brock, Thomas Huddleston, Born Jan 17 1808 in Overton Co. Tennessee, Died May 16 1878 in Montgomery Co. Kansas

Source: https://www.tribalpages.com/tribe/familytree?uid=kimkdm&surname=Brock