There is quite an interesting "Catholic Answers" page at :-http://www.catholic.com/library/Mary_Ever_Virgin.asp on this, comparing the beliefs of various different faiths;
Most Protestants claim that Mary bore children other than Jesus. To support their claim, these Protestants refer to the biblical passages which mention the "brethren of the Lord." As explained in the Catholic Answers tract Brethren of the Lord, neither the Gospel accounts nor the early Christians attest to the notion that Mary bore other children besides Jesus. The faithful knew, through the witness of Scripture and Tradition, that Jesus was Marys only child and that she remained a lifelong virgin.
An important historical document which supports the teaching of Marys perpetual virginity is the Protoevangelium of James, which was written probably less than sixty years after the conclusion of Marys earthly life (around A.D. 120), when memories of her life were still vivid in the minds of many.
According to the world-renowned patristics scholar, Johannes Quasten: "The principal aim of the whole writing [Protoevangelium of James] is to prove the perpetual and inviolate virginity of Mary before, in, and after the birth of Christ" (Patrology, 1:1201).
To begin with, the Protoevangelium records that when Marys birth was prophesied, her mother, St. Anne, vowed that she would devote the child to the service of the Lord, as Samuel had been by his mother (1 Sam. 1:11). Mary would thus serve the Lord at the Temple, as women had for centuries (1 Sam. 2:22), and as Anna the prophetess did at the time of Jesus birth (Luke 2:3637). A life of continual, devoted service to the Lord at the Temple meant that Mary would not be able to live the ordinary life of a child-rearing mother. Rather, she was vowed to a life of perpetual virginity.
However, due to considerations of ceremonial cleanliness, it was eventually necessary for Mary, a consecrated "virgin of the Lord," to have a guardian or protector who would respect her vow of virginity. Thus, according to the Protoevangelium, Joseph, an elderly widower who already had children, was chosen to be her spouse. (This would also explain why Joseph was apparently dead by the time of Jesus adult ministry, since he does not appear during it in the gospels, and since Mary is entrusted to John, rather than to her husband Joseph, at the crucifixion).
According to the Protoevangelium, Joseph was required to regard Marys vow of virginity with the utmost respect. The gravity of his responsibility as the guardian of a virgin was indicated by the fact that, when she was discovered to be with child, he had to answer to the Temple authorities, who thought him guilty of defiling a virgin of the Lord. Mary was also accused of having forsaken the Lord by breaking her vow. Keeping this in mind, it is an incredible insult to the Blessed Virgin to say that she broke her vow by bearing children other than her Lord and God, who was conceived through the power of the Holy Spirit.
The perpetual virginity of Mary has always been reconciled with the biblical references to Christs brethren through a proper understanding of the meaning of the term "brethren." The understanding that the brethren of the Lord were Jesus stepbrothers (children of Joseph) rather than half-brothers (children of Mary) was the most common one until the time of Jerome (fourth century). It was Jerome who introduced the possibility that Christs brethren were actually his cousins, since in Jewish idiom cousins were also referred to as "brethren." The Catholic Church allows the faithful to hold either view, since both are compatible with the reality of Marys perpetual virginity.
Today most Protestants are unaware of these early beliefs regarding Marys virginity and the proper interpretation of "the brethren of the Lord." And yet, the Protestant Reformers themselvesMartin Luther, John Calvin, and Ulrich Zwinglihonored the perpetual virginity of Mary and recognized it as the teaching of the Bible, as have other, more modern Protestants.
The rest is worth a read.
Most Protestants claim that Mary bore children other than Jesus. To support their claim, these Protestants refer to the biblical passages which mention the "brethren of the Lord." As explained in the Catholic Answers tract Brethren of the Lord, neither the Gospel accounts nor the early Christians attest to the notion that Mary bore other children besides Jesus. The faithful knew, through the witness of Scripture and Tradition, that Jesus was Marys only child and that she remained a lifelong virgin.
An important historical document which supports the teaching of Marys perpetual virginity is the Protoevangelium of James, which was written probably less than sixty years after the conclusion of Marys earthly life (around A.D. 120), when memories of her life were still vivid in the minds of many.
According to the world-renowned patristics scholar, Johannes Quasten: "The principal aim of the whole writing [Protoevangelium of James] is to prove the perpetual and inviolate virginity of Mary before, in, and after the birth of Christ" (Patrology, 1:1201).
To begin with, the Protoevangelium records that when Marys birth was prophesied, her mother, St. Anne, vowed that she would devote the child to the service of the Lord, as Samuel had been by his mother (1 Sam. 1:11). Mary would thus serve the Lord at the Temple, as women had for centuries (1 Sam. 2:22), and as Anna the prophetess did at the time of Jesus birth (Luke 2:3637). A life of continual, devoted service to the Lord at the Temple meant that Mary would not be able to live the ordinary life of a child-rearing mother. Rather, she was vowed to a life of perpetual virginity.
However, due to considerations of ceremonial cleanliness, it was eventually necessary for Mary, a consecrated "virgin of the Lord," to have a guardian or protector who would respect her vow of virginity. Thus, according to the Protoevangelium, Joseph, an elderly widower who already had children, was chosen to be her spouse. (This would also explain why Joseph was apparently dead by the time of Jesus adult ministry, since he does not appear during it in the gospels, and since Mary is entrusted to John, rather than to her husband Joseph, at the crucifixion).
According to the Protoevangelium, Joseph was required to regard Marys vow of virginity with the utmost respect. The gravity of his responsibility as the guardian of a virgin was indicated by the fact that, when she was discovered to be with child, he had to answer to the Temple authorities, who thought him guilty of defiling a virgin of the Lord. Mary was also accused of having forsaken the Lord by breaking her vow. Keeping this in mind, it is an incredible insult to the Blessed Virgin to say that she broke her vow by bearing children other than her Lord and God, who was conceived through the power of the Holy Spirit.
The perpetual virginity of Mary has always been reconciled with the biblical references to Christs brethren through a proper understanding of the meaning of the term "brethren." The understanding that the brethren of the Lord were Jesus stepbrothers (children of Joseph) rather than half-brothers (children of Mary) was the most common one until the time of Jerome (fourth century). It was Jerome who introduced the possibility that Christs brethren were actually his cousins, since in Jewish idiom cousins were also referred to as "brethren." The Catholic Church allows the faithful to hold either view, since both are compatible with the reality of Marys perpetual virginity.
Today most Protestants are unaware of these early beliefs regarding Marys virginity and the proper interpretation of "the brethren of the Lord." And yet, the Protestant Reformers themselvesMartin Luther, John Calvin, and Ulrich Zwinglihonored the perpetual virginity of Mary and recognized it as the teaching of the Bible, as have other, more modern Protestants.
The rest is worth a read.