Where do you come up with this stuff?
To the best of my knowledge, Cole Younger, nor any of his brothers, were ever members of any "Union affiliated Militia" nor a member of the Missouri State Guard (sorry Archie).
His father (Henry Washington Younger), was a union man, in the sense that he wasn't for succession, but he was a southern man to the core, as Cole said of his family and father, "naturaly we were Southerners in sympathy and fact." Cole's mother was Bursheba Fristoe, of Independence, Mo. Her maiden name may ring a bell with some readers, as I have pointed out on many occasions that better than 35-40 percent of Quantrill's "core" guerrillias were all related, most of which through ties with the Fristoe family.
Henry Younger had a contract with the U.S. Gov. for mail delivery in Jackson County, Mo. and was one of the weathiest men in that part of the state. He owned a large herd of horse for that mail delivery, but they were stolen by ks. jayhawkers, as well as as meechandism from a store the Younger's owned. Henry went to Kansas City to meet with the State Militia to see if anything could be done, and on his way home was murdered about a mile outside of Westport, Mo. by Mo. State Militia, under the command of Capt. Irvin Walley, in July of 1862. This is the event that led Cole at age 17 or18, along with his cousin, John Jarrette, to join Quantrill, as one of Q's earliest recruits, later that fall. Cole's next youngest brother, Jim, didn't join Q until 1864. Cole's other brothers Bob and John, were too young to fight in the war. (But Bob was old enough to rob banks by 1876).
I agree that Q and other guerrillias waged war against Union civilians, it's one reason why the guerrillia war in MO. is sometimes referred to as the "Household War."
The book, "The Story of Cole Younger, by Himself" is available on line.
I, by no means believe everything he says; I'm sure there is a fair amount of bias in his writing, and he sometime gets his dates wrong, but he was in his 60's, after he got out of prison, but it's fairly typical of the reminiscent writing of the period.