I read it in a book titled Grey Ghosts. It was about the Confederate guerilla warfare units along the Kansas (Jayhawkers)-Missouri border. Among those was Quantrill’s Raiders led by none other than Lt Col William “Bill” Quantrill. Two soldiers of that unit were Frank and Jesse James. Along with them was Tom Little. These raiders would often loot the Union to bankroll operations and it is here Frank and Jesse learned the trade of bank robbing that would earn them infamy as the continued on long after the war ended. Those raider groups were a ‘who is who’ of notorious outlaws and included the Cole Younger gang. I cannot recall, I’ll have to get the book out, but I believe Jesse married Tom’s sister? Tom was hanged by an angry mob after one botched robbery.

Here is some more info: http://en.wikipedia.org/wiki/Quantrill's_Raiders

http://en.wikipedia.org/wiki/Jesse_James_1847