Mary was a virgin before, during, and after the birth of Jesus. This is known as the doctrine of the perpetual virginity of Mary. By the miraculous event of the Annunciation, the Holy Spirit overshadowed Mary and she conceived and bore a Son, named Jesus. Though this is a mystery, it is totally logical to conclude this theological point. A mystery is a divine truth that is revealed but not fully explainable. The chief reason it is not fully explainable is because of language. When we speak of divine truths, which are infinite, we have only finite language to explain them. The very fact that it is finite indicates a limit. We can explain divine truths at times only by analogy because of this limitation.
Our limitations do not mitigate the theological fact of the Virgin Birth. For one thing, the Nicene Creed is specific regarding Christ’s origin. We profess in the creed, “I believe in Jesus Christ His only Son, our Lord who proceeds from the Father.” Mary became the vehicle in which the Holy Spirit brought about Incarnation. The Second Person of the Blessed Trinity, who exists at all times with the First and Third Persons, takes flesh from the Virgin Mary. The fusion of the two natures in one divine person is called the hypostatic union. Since this did not occur by man, the virginity of Mary remained intact.
St. Joseph was the chaste foster father of Jesus. He was the guardian of the holy family and spouse of Mary. It is the doctrine of the church that the marriage between St. Joseph and Mary was true but was not consummated in the carnal sense. In the scriptures, the only reference to the relations of Jesus is by way of the term adelphoi. “Adelphoi,” besides meaning brother, can also be translated to mean uncle, nephew, or cousin. Genesis 11:27 tells us that Abraham was the brother of the father of Lot, which made him his uncle. Ancient Hebrew and Greek did not have a word for “uncle” or “nephew” or “cousin.” The word “brother” was used in the same way we use the word “relative” today. Genesis 14:12, 16 (in the King James Version) refers to Lot as Abraham’s “brother” (ach in Hebrew or adelphos in Greek). When reading the modern English translation of the Bible, James is referred to as “brother of Jesus,” but not “son of Mary.” You can only conclude then that the second meaning of the word, which is “cousin,” is the appropriate translation.
There is no reference to any sibling of Jesus at the foot of the cross with His mother Mary. Since Mary’s cousins were mentioned, it would have also been appropriate for the evangelists to mention Jesus’ siblings by name. Since they are mute on this, it is determined he had no other brother or sister. Hence, Mary was a virgin before, through, and after the birth of her only Son, Jesus Christ.