Marian and Don,
Rose Mary Lankford has information on both Nathan Kerr and William Kerr with sources in her "The Encyclopedia of Quantrill's Guerrillas" that she self-published. The information is on pages 130 and 332.
Rose Mary monitors this forum and we should hear from her on the Kerrs soon. If she should be away for a time I could quote it for you, but I would prefer to let Rose Mary have a chance to speak to this herself.