I am looking for information on the move of the John Corkill family from the Isle of Man to Henry County, Illinois.

My second great-grandfather, John James Corkill (1851-1914) came to the US with his father, John Corkill (approx. 1820 - 1894), and siblings (Margaret, Eleanor Jane, Mary) after the death of his mother, Margaret Kermode (1821 - 1865) landing in Galva, Illinois.

Today I found a marriage record for the elder John Corkill here in the US that states that his father was Robert Corkill and his mother Esther Colkate. I realize that the maiden name for Esther is probably not accurate. This is truly the only information that I have on the elder John Corkill however.

I am wondering if anyone is familiar with family of the elder John Corkill? His birthdate of 1820 is an estimate from census records. I am probably missing something really obvious but I can't seem to sort it out in my mind.