Levi's service record card shows he was DISCHARGED by S. O. (Special Order) No 198 in Nov 1862, as some others were:
http://www.sos.mo.gov/TIF2PDFConsumer/DispPDF.aspx?fTiff=/archives/AdjutantGeneral/Civil_War/ServiceCards/s835/0115.tif&Fln=S30446.pdf
William's shows he was MUSTERED IN April 1862:
Neither card indicates that they died.