Yeah... people are kind of sheltered that way.
Technically James was Jesus' half-brother. (You know, with Diety on one side of the family and all)
Some of the fluff from Da Vinci code comes from a book called "Holy Blood, Holy Grail" which makes some pretty unflattering accusations about the Christian faith. Da Vinci Code was even close enough to the message of that book that the authors of it tried to sued for eleventy-billion dollars. But they lost. And the author of the Da Vinci code, I heard he swims around in a big vault of money like Scrooge McDuck.
Anyway, the book (Holy Blood, Holy Grail) accuses early christians of taking Mary Magdaline (who some purport is the wife of christ), while she was pregnant, and hiding her among the germanic tribes of europe, because it conflicted with thier whole 'Jesus is Lord, much better than us normal people' thing. So Jesus has a bloodline in Europe, and all of his descendants have been hidden (killed?) by the catholic church.
Or something like that. Hopefully someone around here is an expert, and can correct anything I said wrong.
-kv