From these verses, it appears obvious that Joseph and Mary had sex. Why does the Catholic Church teach otherwise? What would be wrong with acknowledging that they did? In what way would the fact that Mary had normal conjugal relations make her any less of a person?
The reason is because in the Greek, the term being translated “until” has different connotations than in English. Depending on where it’s found, this same generic conjunction is translated “to,” “unto,” “as far as,” “even,” “till,” and “until.” So we see it in phrases like, “least to the greatest,” and “I say unto you.” It’s not a perfect translation, which is where the confusion comes in.
blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=G2193&t=KJV
Even when it means “until,” it sometimes means, “until that point and not after,” and other times, it’s just used as sort of a narrative point. In the OT (1 Samuel 15:35), we hear: “Until the day Samuel died, he did not go to see Saul again, though Samuel mourned for him.” Does this mean that on the day Samuel died, he went and say Saul? No. It means, even up to the point that he died, he didn’t see him. There’s no suggestion whether he saw him or not afterwards. (Incidentally, he did, in 1 Samuel 28:13-14, but that’s not implied by the “until”). Granted, that’s in Hebrew, but the same principle holds true in the Greek.
As for the rest of your question, marital sex isn’t a sin, but those willing to give up the possibility of sex for God are praised for it. Additionally, Mary is the Ark of the New Covenant, and as the Old Ark was not to be touched by man, as Uzzah found out the hard way in 2 Samuel 6:1-8.
Mary’s status as Virgin is prophesied in Isaiah 7:14, but note that in neither Matthew nor Luke’s Gospel do we find Mary (or Joseph) being **told **not to have sex. There’s not just a lack of instruction to remain *perpetually *a Virgin, we don’t find the angel telling her even to remain a virgin *until Jesus is born. *And remember, she married Joseph in the interim, as the verse you cited points out.
So why was she even a virgin prior to Jesus’ birth? There’s two options: either the angel instructed her to remain a Virgin (and it just wasn’t recorded), or more likely, she’d taken a vow of perpetual chastity.
We see a hint of that in the Gospel, in Luke 1:34, when Mary asks, “How can this be, since I have no relations with a man?” If Mary was about to be married, and the angel comes and says, “you’re gonna bear the Messiah!” a normal bride-to-be wouldn’t have to ask, “But how?” Because a normal bride-to-be is intending upon having sex. To the extent that the Bible suggests an answer to why Mary was a virgin prior to Jesus’ birth, this is that answer.
Jesus describes this type of vow in Matthew 19:12:
For there are some eunuchs, which were so born from their mother’s womb: and there are some eunuchs, which were made eunuchs of men: and there be eunuchs, which have made themselves eunuchs for the kingdom of heaven’s sake. He that is able to receive it, let him receive it.
A eunuch is someone *incapable *of having sex. Jesus is using some pretty irretractable language - not just a hold-out-wait-and-see, but a give-it-up-for-good. So Jesus considers the highest form of devotion to Him the kind of devotion that will forgo the earthly marital pleasures to which we’re entitled, just to focus more on the Kingdom of Heaven. St. Paul desires something similar in 1 Corinthians 7:7-9:
I would like everyone to be like me [celibate], but each has from God a particular gift, some in one way, others differently. To the unmarried and the widows I say that it would be good for them to remain as I am, but if they cannot control themselves, let them marry, for it is better to marry than to burn with passion.
Paul even ***requires ***the widows supported by the community (something like nuns) in 1 Timothy 5:11 to be celibate. Note that these celibate women needed to be supported, because women in the 1st century generally weren’t able to support themselves. So they were either supported by the community (as in the 1 Timothy 5 example) or supported by a man willing to abide by their vows (usually an older widower, just happy to have the companionship). It is into this latter category which the early Church claimed that Mary belonged.
I suppose that my question is: if Mary is the most blessed of all women, and this status is related to her intensely deep faith, why are you surprised that she fits this category of celibates? And secondly, if not for a vow of celibacy, how do you explain the strange question Mary asks, and her and Joseph’s refusal to engage in marital sex even prior to the birth of Christ?