From a family tree sent to my brother from our cousin Will Cretney in Cleveland Ohio. It traces his fathers line to your James Cretney and Margaret Farragher, his birth date quoted as1743 and carries back to John Cretney 1686 and Abigail Gell then Oates Cretney 1647( LDS has Mrs. Oates Cretney 1645 ) then Finlae Cretney 1606 and Mary Oates.
Most of this information was supplied by Margaret Cregeen of Orchon and Noreen Cottier of Peel IOM.
You can check this on LDS site Search For Ansestors. If you want to find Brothers and Sisters go to right hand side of page type in Fathers and Mothers names nothing else then press search then scroll down to bottom of the page that comes up, click enter on the word 'matches' this will then give all the brothers and sisters, some will be repeated because they are listed on more then one film.

Hope this helps.

Regards Richard