That's not quite right. When used with the genitive of the neuter [not "neutral"] relative pronoun, as it is in Matt 1:25, it is technically an improper preposition of time, not a conjunction.
Thus, when one looks at the actual greek, there is not a question that Joseph knew Mary.
You've never taken any Greek, or you would never have called a neuter pronoun a "neutral" pronoun. The prepositional usage of the term [hews] is ambiguous between (1) up to but not excluding continuation of the action or (2) up to but not after, as I pointed out in #1233. Nothing in Thayer's (or any credible Greek lexicon) shows that it should be taken one way rather than the other in Matt 1:25. Consider how Matthew uses this term in 5:18, where he says, "For truly I say to you, until heaven and eart pass away, not the smallest letter or stroke shall pass away from the Law, until all is accomplished." Jesus is not saying that parts of the Law will be destroyed when everything has been accomplished. Likewise, the usage of this term with the sense that does not exclude continuation of the action can be seen in Matt 10:23; 11:12; 11:23, and many other places.
-A8
Just saying what the lexicon said. Look it up. It specified the verse. I believe that they do use Thayers in that case (check the link I provided).
I have also taken Greek. Am I not allowed to make a typo? It has been about 5 years, but I've taken Greek. I will admit to being a bit rusty on it though which is why I looked it up specifically for that verse in a lexicon. (It's about midway down the page if I recall correctly, subpoint a to a B point.
Considering the context of firstborn and Jesus's brothers and sisters being mentioned in Scripture, it is a stretch to say that Mary and Joseph did not consumate their marriage and have children together. Her perpetual virginity was a later doctrine (as are most Marian doctrines- some coming from "Mary's" lips themselves).