The other Corkill (William) aged 22 in the 1870 census living in the same household with John might not have been bapt in Maughold.
The only one I can find in Maughold records of the right age is: William Illeg son of James Corkill & Margaret Clague bapt Maughold 1 Oct 1848. - His parents married 2 Feb 1850. James was a Smith, the son of James Corkill, Mason, and both bride and groom were living at Dreem Scarrey Maughold.
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