The question of whether or not Mary gave birth to other children besides Jesus is one that has been debated throughout the history of the church. Passages in which the other children of Mary are mentioned are Matthew 12:46-50; Matthew 13:55; Mark 6:3 (mentioning sisters as well as four brothers); Luke 8:19-20; John 2:12; John 7:3-10; and Acts 1:14. Several interpretations of these passages were given by early church leaders. Epiphanius believed they refer to the sons of Joseph by a previous marriage. Jerome said they are cousins. Helvidius believed that they are the sons of Joseph and Mary (young half-brothers of Jesus).
There are several reasons to prefer Helvidius’s view. In the first place, it is the simplest and most natural interpretation of the text. If Mary was so much younger than Joseph that he had a large number of children by an earlier marriage while refraining from a normal marital relationship with her, why would children from an earlier marriage be mentioned repeatedly in close connection with Mary without any indication that they were step-brothers and sisters? It seems most likely that Luke’s reference to Jesus as Mary’s “firstborn” (Luke 2:7) and the statement in Matthew 1:24-25 (“Joseph arose from his sleep, and did as the angel of the Lord commanded him, and took her as his wife, and kept her a virgin until she gave birth to a Son; and he called His name Jesus”) implies that she and Joseph had a large natural family following the Savior’s birth. This, after all, would be the normal and honorable pattern within Jewish culture.
The view that the brothers and sisters (Greek: adelphos, adelphe) mentioned in these passages are actual brothers and sisters confirms Paul’s references to James as “the Lord’s brother” in Galatians 1:19 and to “The Lord’s brothers” in 1 Corinthians 9:5. If they were cousins rather than brothers, Paul would have used the Greek word for “cousins” (anepsioi; see Colossians 4:10).
In light of these factors, those who would depart from the simplest and most natural meaning of the text carry the burden of proof. In our view, the reverence for celibacy and the exaltation of Mary that occurred within the early church is more likely an explanation for Epiphanius’s and Jerome’s interpretations than genuine historical fact.