23“Behold, the virgin shall be with child,
and shall give birth to a son.
They shall call his name Immanuel,”
which is, being interpreted, “God with us.”
24Joseph arose from his sleep, and did as the angel of the Lord commanded him, and took his wife to himself; 25and didn’t know her sexually until she had given birth to her firstborn son. He named him Jesus.The biblical text makes it clear that Jesus was born of a virgin. First, there is the visitation of the angel to Joseph announcing that his betrothed would give birth to a boy by the work of the Holy Spirit (Matt 1:20-25). Second, the text indirectly teaches that Jesus was not born of Joseph, saying Jesus himself, when he began to teach, was about thirty years old, being the son (as was supposed) of Joseph (Luke 3:23). Third, Luke records an interchange between the angel Gabriel and Mary, in which the angel tells her that she would give birth to the Son of God through the Son of God (Luke 1:26-35). None of these verses, however, speaks to the question of whether Joseph and Mary had sexual relations after the virginal birth of Jesus.
It has been in the tradition of the Roman Catholic Church and the Eastern Orthodox Churches that Mary was a virgin during her entire life and that the brother and sisters of Jesus (Matt 13:55-56) were either cousins of Jesus or they were from a former marriage of Joseph, making them half-brothers and half-sisters. If, in fact, the text does not intimate in any way that the siblings were cousins and if they were male children of Joseph, a problem arises in that Jesus would not have been the heir to the throne of David.
Fortunately, the author Matthew provides a very important statement that solves this problem for us. The apostle Matthew makes it plain that Mary was not a perpetual virgin after the birth of Jesus. The text reads very clearly that Joseph and Mary had sexual relations after the birth of Jesus since it says he did not know her sexually until Mary had given birth (Matt 1:25). An additional argument is rarely mentioned, namely, that is, Jesus was the firstborn son of Mary. Had there been no subsequent brothers, this would be an unlikely comment to make.