Several New Testament passages refer to Jesus' siblings. In Matthew 13:55-56, villagers are skeptical of Jesus' powers, saying: "Is not this the carpenter's son? ...Are not his brothers James and and Joseph Simon and Judas? Are not his sisters with us?" The first-century Jewish historian Josephus also refers to James, the brother of Jesus.
Above: Artists' rendering of the ossuary inscription.
Historically, many Catholic scripture experts have contended that the Greek word "adelphos," used in the New Testament passages which describe Jesus' brothers, can mean a cousin, not necessarily a blood brother. The Aramaic inscription on the ossuary of James uses the word "akhui" for brother. According to Protestant scholar Ben Witherington III, both the Aramaic word "akhui" and the Greek word "adelphos" usually refer to a blood brother. Both languages have other words for male cousins.
Eastern Orthodox Christians reconcile the discrepancy by affirming that Joseph had children by a previous marriage; these would have been Jesus' step-siblings nominally, if not biologically. This view is not incompatible with Catholic teaching, but is not widely held by Catholics. Some Catholics refer to Mark 6:3, where Jesus is called the "son of Mary"--not, as would be expected, the "son of Joseph." That Jesus is called "son of Mary," they say, supports the Catholic belief that Mary conceived Jesus through the power of the Holy Spirit and that Joseph was a foster-father entrusted with Jesus' care.
The common Protestant view is that Mary was a virgin before Jesus' birth, but that afterwards she and Joseph had natural children, who would have been Jesus' younger siblings. In Matthew 1:25, Jesus is called Mary's "firstborn son," an expression which many contend was used by Jews only if other children were born after the first one; otherwise, "only son" would have been used.
The Catholic belief in Mary's perpetual virginity is closely tied to one of the few ex cathedra--infallible--teachings of the Church, that of Mary's bodily assumption into heaven. In Munificentissimus Deus, Pope Pius XII declared that "the Blessed Virgin Mary's bodily Assumption into heaven--which surely no faculty of the human mind could know by its own natural powers, as far as the heavenly glorification of the virginal body of the loving Mother of God is concerned--is a truth that has been revealed by God and consequently something that must be firmly and faithfully believed by all children of the Church."