The only child of Conrad's that I have the name of is Thomas A. If I find any others I will surely let you know.
I don't think that Jacob moved to Amherst Co. but rather the county line moved or changed as new counties were formed. As close as I can figure Jacob and much of his family lived on Tayor Creek which flows into the Rockfish River. Taylor Creek runs along the southwestern boundry of what is now Nelson and Albermarle Co. Nelson was formed from Amherst Co. in 1808. Amherst was formed from Albermarle Co. in 1761 and Albermarle was formed from Goochland in 1744. Have you found an Amherst Co. document connected to Jacob?