Isaac Marion Whitney served as a Captain until the Battle of Bentonville when he was breveted to Major for leading the battle due to his commanders being injured.  He resided most of his life in Walker and Fayette Counties in Alabama and had both a half brother, a brother-in-law and a brother who also served in his unit.  His wife was Elizabeth Ann Baker and his parents Hiram C Whitney and Minerva Jones.  His brother, Elhannan William Whitney served in the same unit and was shot and given a disability, later going into cavalry service as a sergeant with his step father Thomas L. Reed in the 8th Alabama Cavalry.  His half brother Reuben Chatman Reed later enlisted in the 28th Alabama Infantry, as a corporal and at the end of the war was a captain.

https://www.findagrave.com/memorial/47253880/isaac-marion-whitney