That's right - they did say that at some point in the movie, and I vaguely remember that this was the case from HB, HG, as well. Supposedly, Mary M hopped on a fast boat to France in the immediate post-crucifixion period, either with or without a very-alive Jesus, and established the Merovingian royal bloodline - I think. I can't remember if the Merovingians already existed and they intermarried, or if they were the Merovingians. Anyway, whether or not historical Jesus survived the crucifixion, it's certainly plausible that he might have descendants - provided you are willing to accept a number of heretical/practical-seeming conclusions prior to such a point.

Um, yeah. Obviously, I'm still more interested in this stuff than I thought. Maybe I need to go read some more crackpot theological theorizing to calm my frenzy.