Frank F. and Francis F. Pitre appear to be twins, although I'm not sure if Francis F. is a male or female.
Per the below census records Frank and Francis are twin brothers.
"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MJZW-FNC : 14 December 2015), Frank Pitre in household of Henry Pitre, Crete, Will, Illinois, United States; citing sheet 21B, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 1,820,414.
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K4P8-GDS : accessed 1 October 2016), Frank Pitre in household of Ruby Pitre, Ward 4, Grand Haven, Grand Haven City, Ottawa, Michigan, United States; citing enumeration district (ED) 70-13, sheet 3A, family 45, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 1808.