Confederate companies had a 1st (Orderly) Sergeant, and he was the top dog. Then there were four duty Sergeants, 2nd through 5th. I'm not sure, but
I don't believe there was any seniority involved. Numbers were based on where they formed up as a Company. The 2nd & 3rd Sergeants were assigned to the 2nd Platoon with the 1st & 3rd Lieutenants, the 4th & 5th to the 1st Platoon with the 2nd Lieutenant. [Hardee's Manual] Others on this board may know more on this
subject.

Confederate companies were alloted 4 Corporals, 1st through 4th and I would believe they were assigned along with the 2nd through 5th Sergeants respectively.
Federal units had 8 Corporals.