My great grandfather Edward James Cain (1837-1884) had an older brother named William baptised 4 Mar 1821 at Lonan (I think), IOM. I have not researched this line. However their younger sister Jane (1824-1867), who married a Mr Grady, died in Albany, USA in 1867. It is just possible William also immigrated to USA.
They are the children of John Cain (1779-1841) and Jane Crennell (ca 1796-1873)