Sincock was born in September 1887 at Barkerville, British Columbia, a boomtown developed during the Cariboo Gold Rush.

[1] His father, Samuel John Sincock, was an immigrant from Cornwall, England, who originally settled in the Copper Country of Michigan's Upper Peninsula and moved to British Columbia in 1877, where he engaged in prospecting and placer mining.

[5] By the time of the 1900 United States Census, Sincock was living in Laurium, Calumet Township, in Michigan's Upper Peninsula with his mother Mary, five siblings, and grandfather William Higgins.

[13] It took 47 years for another British Columbia native, Bob Alexander, to make his major league debut with the Baltimore Orioles in 1955.

[13][14] At the time of the 1910 United States Census, Sincock was living with his mother, grandmother, and a sister at Laurim in Calumet Township, Michigan.

[15] In a draft registration card completed in June 1917, Sincock stated that he was living in Grand Forks, North Dakota, where he was employed as the manager of the new business department for the Red River Power Co.

[17] At the time of the 1930 United States Census, Sincock was living in Chicago and employed as a teacher in a public school.

[19] In his later years, Sincock was employed as the manager of the Douglass House, a hotel in downtown Houghton, Michigan.