The only reason I'm even posting here is because I think Legolas' response is not as complete as it could/should be in pointing out your misreading of the Bible.

From a theological perspective, Matthew (i.e., the author of the Gospel; whether or not that is really Matthew is another theological dispute) wants to emphasize that when Christ is born, Mary is STILL a virgin. She wasn't just a virgin upon conception; she was still a virgin at the moment of birth, which to Matthew's perspective is important to fulfill the prophecy of Isaiah.

To extrapolate from a phrase like "and Joseph did not know Mary prior to the time when she bore a son" that he did consummate the relationship afterwards, while likely in the context of really any healthy marriage whatsoever, is not a logical consequence of the statement. The Koine is clear where the English might not be:

και ὀυκ ἐγινωσκεν ἀυτην ἑως ὁυ ἐτεκεν υἱον

The verb is in the imperfect, which shows a past ongoing action (he was not knowing) all the way up until (ἑως ὁυ) she had (aorist - simple one time event) a son. No implication is made regarding what may or may not have happened afterwards.