I found the following 1911 census from Ontario, Canada, which indicates that the family went from Chicago to Canada in 1906 and then returned to Chicago between 1911 and 1915 when William was born in Chicago. From other sources I found that Edward was born 6 June 1904 in Chicago.
1911 / Ontario / Toronto West / 9 Toronto / page 1
Porter J. Andrew M Head M Sep 1868 42; born Ontario; Plasterer Porter MargaretF Wife M Sep ?31; born Ontario Porter John M Son S Oct 1898 12; born USA; emigrated 1906 Porter James M Son S Jun 1900 11; born USA; emigrated 1906 Porter Louise F Daughter S Nov 1900 10; born USA; emigrated 1906 Porter Edward M Son S Jun ? 7; born USA; emigrated 1906 Porter Joseph M Son S Nov 1909 1; born Ontario Porter Margaret F Daughter S Apr 1911 10/12; born Ontario