I am descended from Russell's half-sister Adeline Matthews Moore and have a bit of information about Francis Brown Matthews to chime in with. "Madison County, Missouri, Cemeteries, Vol. 1" notes that he was married to 1) Nancy Ann Skaggs 9 January 1866. 2) Annie Gale Maze. 3) Lillie Tharp.
Geraldine Sanders Smith, in her book "Civil War Soldiers of Madison County, Missouri (and Surrounding Counties)" shows him marrying Annie Gale Maze 23 April 1907 and Mrs. Lillie Thomas Tharp 1 December 1914. Since he's not a direct ancestor, I've not bothered to look for the original records to verify these names and dates.