I don't know that that is so. Usually, it's said that he had such a high regard for her, being chosen by God, etc. etc., that he wouldn't think of touching her, not that he was unable or something like that.
The reality of Scripture is recorded in Matthew. Also from the ETWN's own web site we find this................
EWTN.com - St Joseph as widower and father of several by his first marriage
Matthew 12:46 ..........
"While he was still speaking to the people, behold, his mother and his brothers stood outside, asking to speak to him. But he replied to the man who told him, "Who is my mother, and who are my brothers?" And stretching out his hand toward his disciples, he said, "Here are my mother and my brothers! For whoever does the will of my Father in heaven is my brother, and sister, and mother."
The most commonly proposed solution to understanding this text in light of the
infallible teaching of the perpetual virginity of Mary is that these "brothers" are kinfolk. A minority solution proposes that perhaps St. Joseph had children by a previous marriage and took Mary as his wife as an older man.
"St. Jerome notes that such a belief is based upon a non-biblical writing and he rejects it. Such an apocryphal idea may represent a sincere attempt to account for this seeming complication."
All I am saying is that the suggestion that Joseph was married previous to being mentioned in Scripture as Mary’s betrothed is completely fictional, and that there is no scriptural evidence, or even a subtle suggestion, that Joseph was married to anyone but Mary.
It is often tempting to try to make Scripture say something it does not say in order to create a theology we like and it seems to me that is exactly the case here. The RCC need an explanation for the brothers and sisters of Jesus so as to explain the perpetual virginity of Mary.
But we should remember a basic principle of scriptural interpretation: “Whenever possible, let Scripture interpret Scripture.” We get into trouble when we try to make God’s Word fit our preconceived ideas or a doctrine we find comforting. The notion of Joseph’s previous marriage is such an idea and has no foundation in God’s Word