If you will go to this site

http://www.rootsweb.com/~mstallah/military/index.html

scroll down until you see "Page One & Two, Civil War Soldiers"

view these pages, your grandfathers brothers are listed by unit. This does not provide the documentation you need but should narrow your search.

It is also my suggestion that you order the service records of these men. That eliminates any confusion. It can be done by a clickable link at the top of this page or by going to

http://mdah.state.ms.us/arlib/refreq_guides.html

George