What makes you think Y is true? There is no evidence. X is an assertion without basis.
Your post 675 calls into question the claim Joseph had a previous marriage by noting said claim is not demostrable from scripture.
The implicit premise of such a question is that the narrative of scripture is exhaustive.
Scripture makes no such claim.
So while one might reasonably claim Jesus had no moles, one can make no such assertion, positive or negative, for say, John the Revelator.