"The names Jacob, John, James, and Shephard all appear in the Bible in the Book of Matthew. Jacob was the father of Joseph who was the father of Jesus Christ. So on Lost, Jacob is Christian's father making him Jack's grandfather.i.e:JACOB SHEPARD!!! This means we can see why Jack is of the utmost importance to the island, Jacob found the island and is making Jack the islands saviour. What strikes me as either important or coincidence is the book of the bible in which this occurs, Matthew which is Jack's name in real life, Matthew Fox!!!"