I’m back doing genealogy and just found a 3X uncle who died of small pox while interred in a Union prison camp in Chicago. I have a bunch of ggg uncles who fought for the confederacy. My great great grandfather started out in an irregular confederate militia, was captured at Shiloh and then paroled on condition that he join the Union Army which he did.
One of my ancestors did the same. MO militia, captured by Union Army, joined it and went west to fight Indians.