Her name was Annie M Kimball born in Massachusetts c 1856. They had one more child that was not included in your list; Percy Harrison Burrill b. 31 Mar 1887 and her name was confirmed on his marriage certificate. She apparently died between 1887 and 1898 as Joseph re-married an Emma Duncanson in 1898 and had four more children starting in 1901.
George Churchill ( descendant of Joseph )