The Catholic wants the text to say on Thursday night Joseph and Mary "knew" each other and nine months later......
The local Jews identified Joseph, Mary, Jesus, His brothers and sisters as one family. The emphasis of the passage is on Jesus. It's why everything centers around Him.
We already are familiar with the silly challenges of "where does the Bible say sola Scriptura?", "where is there a table of contents in the Bible?", "where does the Bible say 'Rapture'?", and so on. To insist they MUST have a phrase of "children/offspring/sons/daughters of Mary" in order to accept it is just more of the same. I can pretty much guarantee that even if there was such a passage, it would be explained away as a translation error or some other reason. I'm content with just saying we don't know for sure and neither do they. I think the Holy Spirit showed us some things that makes their argument harder to defend, but..it's just not that important to cause huge arguments and dissension.
The Apostles taught the virgin birth of Jesus because it was a fulfillment of critical Messianic prophecy. They didn't say a word about having to believe Mary remained a virgin her whole life and never had anymore children. That was something that some people started spreading hundreds of years later and it was not universally accepted even by those called Early Church Fathers. Like I said before, it's not a hill to die on, but the way some people go on and on, it sounds like some of them would.