I think the notion that Jesus had children (with Mary Magdalene, or various others, for that matter) is rather an old one, if Mr Baigent and Mr Leigh claim to have come up with it themselves, they're either much older than scientific understanding would suggest is possible, or they're as delusional as Mr. Brown (who seems to believe that he wrote History rather than Fiction).
The idea that such a bloodline might have continued isn't much more recent, I don't expect. Shucks, the Roman Catholic Church is founded on the notion that Peter's bloodline continues, it's not much of a stretch from that.
As far as that goes, the idea of a secret heir to
whatever dynasty suddenly popping up and claiming his legacy (to the ill health of the present claimants) is bread and butter of human civilization since shortly after the idea of inheritance was conceived. I wonder if Seth's son Enos worried that Cain's boy might show up and claim his Birthright?
