Since Catholics believe Mary (Jesus's mother) remained a virgin her entire life, how do you explain the mention of Jesus having brothers in Luke 8:19-21 and again in John 7:2-10?First, the passages you cited:
19 Then his mother and his brothers (Gk.: adelphos) came to him, but they could not reach him for the crowd.
20 And he was told, "Your mother and your brothers (adelphos) are standing outside, desiring to see you."
21 But he said to them, "My mother and my brothers (adelphos) are those who hear the word of God and do it."
2 Now the Jews' feast of Tabernacles was at hand.
3 So his brothers (adelphos) said to him, "Leave here and go to Judea, that your disciples may see the works you are doing.
4 For no man works in secret if he seeks to be known openly. If you do these things, show yourself to the world."
5 For even his brothers (adelphos) did not believe in him.
6 Jesus said to them, "My time has not yet come, but your time is always here.
7 The world cannot hate you, but it hates me because I testify of it that its works are evil.
8 Go to the feast yourselves; I am not going up to this feast, for my time has not yet fully come."
9 So saying, he remained in Galilee.
10 But after his brothers (adelphos) had gone up to the feast, then he also went up, not publicly but in private.
We see that the Greek word for "brother" in these passages is adelphos. This word has a variety of meanings. It does not just mean "blood brother". The KJV New Testament Greek Lexicon tells us that adelphos has the following meanings:
- a brother, whether born of the same two parents or only of the same father or mother
- having the same national ancestor, belonging to the same people, or countryman
- any fellow or man
- a fellow believer, united to another by the bond of affection
- an associate in employment or office
- brethren in Christ
- his brothers by blood
- all men
- Christians, as those who are exalted to the same heavenly place
Gen 29:15 And Laban said unto Jacob, Because thou art my brother (LXX, adelphos), shouldest thou therefore serve me for nought? tell me, what shall thy wages be? (note: Jacob was actually Laban's nephew)
2 Sam 1:26 I am distressed for thee, my brother (LXX, adelphos) Jonathan: very pleasant hast thou been unto me: thy love to me was wonderful, passing the love of women. (note: Jonathan was just a friend)
Neh 5:1 And there was a great cry of the people and of their wives against their brethren (LXX, adelphos) the Jews.
Lk 22:32 But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren (adelphos).
Acts 11:1 And the apostles and brethren (adelphos) that were in Judaea heard that the Gentiles had also received the word of God.
Rom 9:3 For I could wish that myself were accursed from Christ for my brethren (adelphos), my kinsmen according to the flesh
Now that we know the word can be used to describe a variety of relationships, the question is whether or not we should consider one of these alternative meanings for the "brothers" of Jesus. Here is when some historical-criticism is helpful.
For one, Jesus was the first born of the family, so these "brothers" (if they were blood brothers) would be younger than him. BUT, in Jesus' day, no younger brother would dare speak to the eldest the way these brothers are speaking to Jesus. They are presuming to give him orders, or to advise him. This simply would not have happened, and his mother surely would not have allowed it!
Secondly, it is widely held that Mary was a widow by the time Jesus began his ministry, or at least by the time it ended. When the father dies, it is the responsibility of the eldest to care for his mother. When the eldest dies, it falls on the second brother. BUT, Jesus gave his mother to John, not to any of his "brothers" (Jn 19:26-27). This too would have been out-of-line if these brothers were his actual siblings.
Finally, it's interesting that Jesus is referred to as "the" son of Mary, instead of "a" son (cf. Mk 6:3). Maybe there's nothing there, but it seems to me that if she had multiple sons, "a son" would have been the more appropriate phrase.
Another reason we know these "brothers" aren't true siblings is because in Mt 13:55 (cf. Mk 6:3) we see that the brothers referenced in Lk 8 and Jn 7 are "James and Joseph and Simon and Judas". But, scripture tells us that at least two of them are actually Jesus' cousins:
- Jn 19:25 says that "Mary, the wife of Clopas" is the Blessed Mother's sister.
- "Mary, the wife of Clopas" is the "other mary" who went to the sepulcher with Mary Magdalene
- This "other mary" is also the mother of James and Joseph (Mt 27:56,61; 28:1; Mk 15:47).
- So, this would make James and Joseph the cousins of Jesus, even tho Mt 13:55 and Mk 6:3 say that they are Jesus' "brothers."
All of this makes it highly unlikely that the "brothers" mentioned in Lk 8:19-21 and Jn 7:2-10 were Jesus' actual siblings. Instead, they were probably close relatives of some kind. I hope that helps.