The Roman Catholic Church teaches the perpetual virginity of Mary; thus it denies that she had other children besides Jesus. ‘The deepening of faith in the virginal motherhood led the Church to confess Mary’s real and perpetual virginity even in the act of giving birth to the Son of God made man. In fact, Christ’s birth “did not diminish his mother’s virginal integrity but sanctified it.” And so the liturgy of the Church celebrates Mary as Aeiparthenos, the “Ever-virgin” (The Catechism of the Catholic Church, 499).
But the truth is that Mary did not remain a virgin after the birth of Jesus, because the Bible teaches that Joseph and Mary did have sexual union after Jesus was born, and she gave birth to other children.
Matthew says that Joseph “took unto him his wife: and knew her not till she had brought forth her firstborn son: and he called his name JESUS” (Matthew 1:24,25). That means that Joseph, after Mary gave birth to Jesus, knew her. Note that it is not written that he never knew her after he took Mary home as his wife, but that he knew her not till she had brought forth Jesus. Thus, after the birth of Jesus, Joseph knew his wife Mary. But let me show you from the Scriptures that Jesus was not the only son Mary gave birth to, for she conceived and gave birth to other children.
● Luke says that “she brought forth her firstborn son” (Luke 2:7), thus if Jesus were her only son he would be called her only begotten son and not her firstborn son.
● Mark says: “And he went out from thence, and came into his own country; and his disciples follow him. And when the Sabbath day was come, he began to teach in the synagogue: and many hearing him were astonished, saying, From whence hath this man these things? and what wisdom is this which is given unto him, that even such mighty works are wrought by his hands? Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him” (Mark 6:1-3)
● Mark says: “There came then his brethren and his mother, and, standing without, sent unto him, calling him” (Mark 3:31).
● John says: “For neither did his brethren believe in him” (John 7:5).
● Luke says in the Acts: “These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren” (Acts 1:14).
● Paul says to the Corinthians: “Have we not power to lead about a sister, a wife, as well as other apostles, and as the brethren of the Lord, and Cephas?” (1 Corinthians 9:5).
● Paul says to the Galatians: “Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days. But other of the apostles saw I none, save James the Lord’s brother” (Gal. 1:18-19).
● The 69th Psalm says about the Christ: “I am become a stranger unto my brethren, and an alien unto my mother’s children” (Psalm 69:8). Therefore, the Scripture even foretold that the virgin who would conceive and give birth to the Christ of God would not remain a virgin because she would give birth to other sons, as the Spirit of Christ said through David: “I am become an alien unto my mother’s children”.