Why does the Bible say that Jesus had brothers if Mary was a virgin her whole life?
There are several verses in Scripture that refer to the “brothers” of Jesus (cf. Mt 12:46; 13:55-56; Mk 3:31; Lk 8:19; Jn 7:1-10; Acts 1:14; Gal 1:19). However, it is not necessary to believe that these “brothers” were actually His siblings.
Remember, the New Testament was written in Greek. The Greek word for “brother” in these verses is adelphos. This word can mean “sibling,” but it is also used in Scripture to refer to those of the same nationality; any man, or neighbor; persons with like interests; distant descendants of the same parents; persons united by a common calling; mankind; the disciples; and all believers.
Considering the broad meaning of the word, we can just as easily say that these “brothers” of Jesus were not Jesus’ siblings but instead were related to Him in some other way. Scripture tells us that at least four of these brothers – James, Joseph, Simon, and Judas – were actually Jesus’ cousins, since their mother was Mary’s sister (cf. Mt 27:56,61; 28:1; Mk 15:47; Jn 19:25).
The customs of the day are helpful here as well. For one, Jesus was the first born of the family, so these brothers would be younger than Him. In Jn 7:1-10 we see them giving Jesus orders and practically reprimanding Him. Yet, in Jesus' day, no younger brother would dare speak to the eldest the way these brothers speak to Jesus.
Also, it was Jewish custom for the eldest son to take care of his mother once his father died. Once the eldest son died, this responsibility fell on the next son, and so on. Yet, Jesus gave his mother to the Apostle John, not to any of His brothers (cf. Jn 19:26-27).
Furthermore, if Jesus had siblings, where were they when Mary and Joseph lost Jesus on the way back from celebrating the Passover in Jerusalem? These siblings certainly would have been traveling with them. Yet, there is no mention of them at all in the account of what happened. Note also that, when Mary and Joseph realized that Jesus was gone, they didn’t go to his supposed siblings, which would have been the logical thing to do. Instead, they looked among their “kinfolk and acquaintances” (Lk 2:44).
Finally, Jesus is referred to in Scripture as "the" son of Joseph and Mary, instead of "a" son (cf. Mk 6:3; Jn 1:45; 6:42). Maybe there's nothing there, but it seems to me that if Mary had multiple sons, "a son" would have been the more appropriate phrase.
All of this explains why Catholics have nothing to fear when they read of the “brothers of Jesus” in Scripture.
Peace of Christ to you,
Director of Religious Education