With all due respect, I do know what RC's believe about Mary, I been conversing with them for 9 months here on FR. You believe that Mary stayed a virgin her whole life, right? This violates the very command that Brian quoted above from God: "Be fruitful and multiply". Along with the command to not deprive your spouse of sexual intercourse. Our bodies belong to our spouses, not ourselves. My belief is that what the Bible clearly shows, after the birth of Jesus the family carried on as any righteous Jewish household at the time and Joseph and Mary had many other children, including James the author of the Bilical book.
I wonder if you've read "Jerome versus Helvidius", a debate on this very subject?
Your belief is clearly wrong and shows that you do not know Scripture. Mary was the spouse of the Holy Spirit not Joseph. Joseph was chosen to serve as a the earthly husband/protector of the Blessed Virgin Mary. Scripture writes that Jesus is called the carpenter's son, Matthew 13:55, yet we know that He is the Son of God, not Joseph. After Christ is found in the Temple at the age of 12 Joseph is not mentioned in Scripture again. Who was Mary's new husband? No mention is made of other children; Luke 2:41-51. No mention is made off Mary remarrying. Jesus is always referred to as the son of Mary, not a son of Mary. The Disciples were older than Jesus, not younger. Due to Jewish custom, younger brothers would not give advice to an older brother. We know that Jesus was Mary's firstborn, which does not mean that others followed, son. If Jesus had brothers and sisters He would not have entrusted the care of His mother to John. You misunderstand the words brethren and brothers to mean blood relation, which it is not. Refer to John 19:25. Mary of Cleophas, the sister of the Blessed Virgin Mary, is the mother of James the Less, Joses and Juda.
Our bodies belong to our spouses, not ourselves.
Our bodies belong to God, not our spouses.
Stating that Jesus had siblings and that Mary had other children contradicts Scripture and is simply wrong. Calvin, Luther and Zwingli also believed in the Blessed Virgin Marys' perpetual virginity. I'm surprised that your conversion classes have failed to have you read the The Protoevangelium of James and Brothers and Sisters of Jesus. Don't allow yourself to be conned into thinking that Jesus had brothers and sisters. Mary gave birth to only one child and remained a virgin her entire life. Don't add to Scripture. If you need more explanation, freep mail me.