I've definitively identified 3 of 4 Earles that were supposedly part of the Palmetto Rifleman (B Company) of the 4th Volunteers: Captain Alexander Campbell Earle of Greenville, Lieutenant Charles Eugene Earle of Greenville, and George Washington Earle of Anderson. The First two were brothers and the third was a first cousin. A.C. went on to lead the Earle Cavalry after the 4th dissolved and moved to Alabama after the war. Charles Eugene committed suicide the day after commanding company B in the unexpected absence of its captain during the first battle of Bull Run. G.W. survived the war and returned to Anderson.
The fourth Earle, Joe, is a bit mysterious. There is a Joseph Earle, cousin of A.C. and Charles Eugene and also from Greenville, but he joined the Charles Artillery Battery, not the 4th Volunteers. He survived the war and died as a sitting U.S. Senator. I've decided to write a fictional character to take his place. I'm going to place him as the son of an abolitionist who is caught in the South at the beginning of the war and poses as Joseph Earle when joining the 4th. This will give me a chance to write a bit of an outsider's perspective of the Palmetto Rifleman and A.C. Earle's Cavalry.
