There are several lengthy writings online concerning the virgin birth and the NIV. This one is a little more succinct.
https://www.febc.edu.sg/v15/article/def_untrustworthiness_of_niv
You mean this argument?
In Luke 2:33 we read, “And Joseph and his mother marvelled at those things which were spoken of him” (KJV). In the NIV, it is like this, “The child’s father and mother marveled at what was said about him.” Do you see the problem here with the NIV? The NIV makes Joseph the father of Jesus!
This is only problematic for the NIV if you ignore the NIV:
In the sixth month of Elizabeth’s pregnancy, God sent the angel Gabriel to Nazareth, a town in Galilee, to a virgin pledged to be married to a man named Joseph, a descendant of David. The virgin’s name was Mary. (Luke 1:26-27)
And then, a little lower down:
“How will this be,” Mary asked the angel, “since I am a virgin?” (1:34)
In my edition of the NIV, 1:26-27 is on page 723, while 2:33 is on 725. They are literally one turn of the page apart. If you read that one or two paragraphs in chapter 1 where Luke calls Mary a "virgin," then you'd have to have the memory of the proverbial goldfish to think the NIV denied the virgin birth by the time you'd read chapter 2.
This isn't a theological issue. It's a cynical accusation levelled by people who think Christians are too stupid to remember what they just read a minute ago.
But the KJV doesn't actually solve this problem:
Now his parents went to Jerusalem every year at the feast of the passover. (2:41)
Parents typically come in pairs. If Mary was Jesus's mother, what
parent did that make Joseph? Well, Mary tells us:
His mother said unto him, Son, why hast thou thus dealt with us? behold, thy father and I have sought thee sorrowing. (2:48)
KJV-onlyists get around this by saying Mary needed to be "corrected"; this is stupid. Did she misremember the circumstances of his birth? Did she forget about the angels? Was
the Virgin Mary denying the virgin birth?
So this argument is ridiculous.
Jesus was, "as was supposed," the son of Joseph (Luke 3:23 KJV). Presumably the details of the virgin birth were not widely known and anyone who could count to nine presumed him to be Joseph's son out of wedlock. Call Joseph Jesus' stepfather, foster father, adoptive father, or what you will: he raised Jesus, taught him the family trade, and had parental authority over him (cf. Luke 2:51). He was,
understood correctly, Jesus's de facto father. That was the role he fulfilled in Jesus's earthly family. Of course, KJV-onlyists have no interest in understanding properly.
Also, it sidesteps your original assertion that Westcott and Hort denied the virgin birth. They had nothing to do with the NIV.