Lee,

I found the following information in Joanne Eakin's and Donald R. Hale's 1993 "Branded As Rebels" published in Independence, MO by Wee Print, p. 113. Eakin and Hale's sources include:
--"Liberty Tribune" newspaper, Clay County, 21 June 1901;
--"Liberty Tribune" newspaper, Clay County, 27 March 1868;
--Don Hoog letter from Cincinnati, OH to Donald Hale 23 February 1970 (probably in possession of Mr. Hale);
--personal correspondence of Neil Block, 400 N. Main, Huntsille, MO 64259;
--John P. Burch, "Charles W. Quantrell: A True History of His Guerrilla Warfare (and etc.)" Vega, Texas: publ. by author, 1923, (page numbers not known and Burch's writing of Harrison Trow's memoir is not indexed; In short, I don't yet know what Trow said about the Devers. Be careful, Trow's memory played tricks on him by 1923 when he dictated his memoirs to Burch.);
--Richard S. Brownlee, "Gray Ghosts of the Confederacy," Baton Rouge: LSU Press, 1958, p. 255 (Brownlee got his information for his famous list of guerrillas in the back of his book from Hoog, and others, but the years of death given are not correct for many on the list.).

All this boils down to this:
--All three Devers evidently rode with George Todd at least during 1864. Some of them may have served earlier under Quantrill, but I'm foggy on that. Todd was killed 21 October 1864 outside Independence engaging Union troops during Price's great Missouri raid, and his guerrillas then served under other leaders. Alexander and Arthur Devers were serving under Oliver Shepherd with a few others formerly of Todd's band and at Mrs. Fox's in north Clay County 30 March 1865 were killed by citizen militia. (Sources for this include the 1901 "Liberty Tribune" article and the 1885 history of Clay County, page 257.) James M. Devers survived his service under Todd and others during the war, but was lynched along with fellow former guerrilla Andy McGuire by a mob at Richmond, Ray County, on 17 March 1868 for his alleged part in the Richmond bank robbery earlier. (One source for this is the 27 March 1868 Liberty newspaper.)

Rose Mary Lankford in her 1999 "The Encyclopedia of Quantrill's Guerrilla's" that she published in Evening Shade, Arkansas on page 57 has more about James' adventures postwar leading up to his lynching.

Sorry I did not speak up sooner. I must have been napping since October when you first posted your query.

Bruce Nichols