Some Christians study the New Testament, read how some of Jesus’s Apostles were called his brothers, and claim that as proof that Mary had other children.
The Catholic Church teaches that Jesus was the only child of Mary and Joseph (CCC 501). It is important to note that the English Bible we study is based on Greek translations. The term “brother” in Greek is adelphos, which can mean a biological sibling, but also includes extended relatives and spiritual brothers.
We see the word “brother” as a “spiritual brother” used in both the Old and New Testament. For instance, in 1 Corinthians 15:6, Jesus appears “to more than five hundred brothers at once.” We can safely assume that Mary did not have five hundred sons in addition to Jesus.
We also know that as Catholics, we all call Mary our Holy Mother. While we are all part of the Mystical Body of Christ, that doesn’t mean we claim to be her biological children or to be physically related to every Catholic who calls the Blessed Virgin their mother. The Catechism of the Catholic Church explains:
Jesus is Mary’s only son, but her spiritual motherhood extends to all men whom indeed he came to save: “The Son whom she brought forth is he whom God placed as the first-born among many brethren, that is, the faithful in whose generation and formulation she cooperates with a mother’s love” (CCC 501).
It is easy to misunderstand parts of Scripture and to take certain parts more literally than necessary. That is why it is important to study what these words mean in the original languages of the Bible and to use the Catechism of the Catholic Church as your guide.