Da Vinci Code & Mary's Descendants 
As the Da Vinci Code fictional story, Many disbelieve, that Mary had descendants through Jesus having children, as inconsistent with their core beliefs in Christianity imputing that if Jesus had children he didnt die on the cross and go to heaven. 
But Jesus having children was prophecied serveral times in Isaiah 
See -
He shall see his Seed - Isaiah 53: 10 
He shall sprinkle his Seed across many nations - Isaiah 52:15
Thus saith the Lord, the Holy One of Israel, and His Maker, ask me of things to concerning MY SONS ... Isaiah 45: 11
...
and so, then the subject cannot be blythly ignored with off point attacks about timing as Jesus having had children before he died on the cross and went to heaven, is not inconsistent with any Christian belief.

The only source for a rational discussion of this is the book, The Jesus Presidents laying it all out vs the off point rants about this or that
and attempting to bad mouth Da Vinci Code's accurate facts in regard to 
the descendants of Jesus.

See Jesus Descendants to Today to Many Readers and ? You ?