The Catholic Church teaches that the mother of our Lord remained a virgin throughout her life. Even though the major Protestant leaders like Luther, Calvin, and Zwingli, staunchly defended the ever virgin Mary along with the Catholic Church, many of their modern day followers criticize this belief, attempting to use the Bible as their proof. Let's investigate.
One claim that supposedly disproves Mary's perpetual virginity is in the opening chapter of Matthew's gospel where it reads, "He had no relations with her until she bore a son". But Matthew, far from sharing information about a married couple's private life, is merely emphasizing that Joseph is not Jesus' biological father. Note that the word until does not necessarily mean that what happens or doesn't happen up to a certain point in time must happen afterward. During the presentation of Jesus in the temple, Luke writes that Anna lived as a widow until she was 84. There is no implication that this octogenarian then tied the knot a second time. After David danced before the Arc of the Covenant, the text says his disgruntled wife Michal remained childless until the day she died. And then?
Regarding the brothers of Jesus mentioned in Scripture, Hebrew and Aramaic had no specific word for cousin, so the word brother or brethren was used. Note in Mark 6 that even though His brothers are mentioned, only Jesus is identified as the son of Mary. No one else is ever called this. St. Paul in Galatians 1 says he spent time with the Apostle James, the brother of the Lord, yet the two Apostles named James are identified in Mark 3 and are not the sons of Joseph. Finally, if Jesus had actual brothers (or more correctly half-brothers) He would have transgressed Jewish practice by not entrusting His mother to one of them.
Since Mary is the new Arc of the Covenant, her purity demanded lifelong virginity, the intent of which was expressed by her "how can this be?" response to the angel Gabriel. Unless her intent was to remain a virgin, a healthy engaged woman of child-bearing age might have asked when, but not how.
In light of the consistent teaching of the Catholic Church, the writings of the Church Fathers, the supporting testimony of traditional Protestantism, and proper Bible exegesis, we might well question the motive for this relatively modern attack on the ever-virgin Mary and ask why.