William S. Crouch and John T. Crouch appear to have been sons of George Crouch of Muscogee County GA. However, since William S. Crouch was only one year old accourding to the 1850 census, he was too young for military service in 1863. In any case, he doesn't appear with George Crouch household in 1860 and may have died earlier.
According to military service files, George Crouch filed a claim for his son, John T. Crouch, who died in the Battle of Gaines Mill VA, June 27, 1862. Mary Jane Crouch of Heard County GA filed a claim for her husband, Thomas W. Crouch, who died at Gettysburg PA, July 2, 1863. Both these men served in Co. "C", 2nd Georgia Regiment.
Since the 1860 census reports the ages of Thomas Crouch and George Crouch as 35 and 45 respectively, it seems quite unlikely that Thomas and William Crouch could have been brothers. Uncle and newphew would seem much more reasonable, if any relation at all.
Copies of military service files are available here --