You might check this fellow out.

Forrest, James
Private—Enlisted in Co. G, 12th Arkansas Cavalry, in Ashley county, Arkansas, December 14, 1863; absent without leave since February 10, 1864.

Confederate Service muster roll records are very incomplete and many mens records fall throught the cracks and are lost.

Most of Wrights command was made up of men who had surrendered at Vicksburg and been paroled back to their home state of Arkansas. Ashley County is a long ways from Craighead Co where you say his two half brothers enlisted.