Most of those potential father-son enlistments if any would likely be found within the first year of the war. In May of 1862 the Confederate forces reorganized. Initial enlistment terms of 3, 6 or 12 months were changed into three years, or for the war. Enforcement of the respective enlistment age range also utilized. At that period of the war those under 18 or over 35 were discharged and sent home. A possible father-son team original enlistment they could have been 19 and 40 something years of age respectively. Son kept... Dad being over 35 was discharged as being "over age". He now being exempt from active field service duty but still could serve in reserves and local home guards. Later in the war when enlistments waned, conscription acts kicked in, as well as expansion of the military service age from 17 to 45. There were folks that volunteered in 1861 that may have been around 40 years old. Discharged in 1862 as being over age, then drafted back into service in 1864.

Hope this helps
Frederick