Psalm 69:8-9 (English Standard Version)
"I have become a stranger to my brothers,
an alien to my mother’s sons.
For zeal for your house has consumed me,
and the reproaches of those who reproach you have fallen on me."
(also treated as Messianic in Romans 15:3 by the apostle Paul)
Since John is the one who is quoting and alluding to Psalm 69 so much:
John 2:17 (Psalm 69:9)
John 15:25 (Psalm 69:4)
John 19:28-29 (Psalm 69:21)
In addition, the context of John 7:3-5 is about his brothers not believing in Him, and then in verses 6-8, it becomes even more clear that John is saying that Psalm 69:8 is about Mary’s others sons. John 7:6, “Jesus therefore said to them, “My time is not yet at hand, but your time is always opportune.” John 7:7, “The world cannot hate you; but it hates me because I testify of it, that its deeds are evil.” Because verse 3 in the same context says, “His brothers therefore said to Him, “Depart from here and go into Judea, that your disciples also may behold Your works which You are doing.” – here is a clear distinction between Jesus’ brothers and Jesus’ disciples. He contrasts between the faith and love of the disciples and the hatred and unbelief of the world. He does the same thing in John 15:25, another quote from Psalm 69. “They hated Me without a cause”. Now the context of the cross and the giving of Mary to John to care of her becomes even more important and more clear that Mary had other children. And then in John 19:27-28, where Jesus says, “Behold, your mother!”, Jesus is clearly connected her with Psalm 69, because his real brothers have disowned Him and been estranged from Him and rejected Him, and hated Him, so therefore, He commits His mother to John. In verse 28 of John 19, the Scripture says, “. . . in order that the Scripture might be fulfilled, said, “I am thirsty”. Psalm 69:21 – with Matthew 27:34, 48, Mark 15:23, 36, and Luke 23:36.
In church history, some people began to make unreasonable deductions about Mary, going beyond Scripture, adding to Scripture, and contradicting Scripture.
These unreasonable deductions led to the whole series of unbiblical traditions about Mary (prayers to her, IC, BA, co-mediatrix, some even calling for co-redemptrix to be defined as dogma) and led to the over-exalting of Mary, the over-emphasis on virginity (even after marriage), and celibacy as a requirement for all ministers in the RCC in church history. It is called a “higher way of holiness”. This implies that married folks cannot attain to a holy life, and it seems to exalt works over grace and faith.
Obviously, Psalm 69:5 is NOT about the Messiah, because He was sinless. (John 8:46; 2 Cor. 5:21; Heb. 4:15, Heb. 7:26; I Peter 1:19-20). This can be understood the same way that 2 Samuel 7:14a is about the Messiah, but 7:14b is not about the Messiah. So, it is possible that Psalm 69:8 is about Mary's others son who are against the Messiah and don't have faith until the resurrection and afterward, but Psalm 69:5 is not about the Messiah.
By the way, a great sermon on Psalm 69 and emotions, including other quotes in Romans 11 and Acts 1, in his series on some of the Psalms in "Thinking and Feeling with God" by John Piper is here.
The apostle John seems to want us to get the connection by looking at Psalm 69 and all the other quotes in his gospel. (and Acts 1 and Romans 11 and 15)
Moreover, "for" in Psalm 69:9 connects it to his zeal; and John is showing the contrast between the faith of the disciples in John 2:12-22 and John 7:3-7 vs. His brothers who, because of their unbelief, are His enemies and "hated Him without a cause". (John 15:25 and alluded to in John 7:7 - the hatred of the world; from Psalm 69:4)
John 7:3-9 :
So his brothers said to him, "Leave here and go to Judea, that your disciples also may see the works you are doing. For no one works in secret if he seeks to be known openly. If you do these things, show yourself to the world." For not even his brothers believed in him. Jesus said to them, "My time has not yet come, but your time is always here. The world cannot hate you, but it hates me because I testify about it that its works are evil. You go up to the feast. I am not going up to this feast, for my time has not yet fully come." After saying this, he remained in Galilee.
One of the ways skeptics attack the resurrection is they say Jesus only appeared in His resurrection to His friends, believers, disciples.
Well, Jesus' brothers were not believing in Him, and so, they were His enemies in this sense, even hating Him, implied here; because they wanted Him to show Himself to the world; and it says the Jews were seeking to kill Him. (John 7:1)
They were His enemies in their unbelief; but they believed at the resurrection and afterward; especially, James (I Cor. 15:7; Galatians 1:19; Acts 15:13ff.)and Jude (writer of the epistle of Jude).
So Christ appeared to some enemies, namely His brothers, and Saul, who became Paul.
A powerful apologetic for the resurrection.
Seems clear that John and Jesus are making this connection between the sufferings of David in Psalm 69, that his own brothers, "my mother's sons are against me"; and also this is prophesied about the Messiah and it happen that way; and so it is clearly implied and alluded to by the way John uses Psalm 69, the connection "for" in verse 9, and the contrast between the faith of the disciples and lack of faith in His brothers in John 2:12-22; then the hatred and unbelief of His brothers in John 7.
Putting it all together, it makes perfect sense why Jesus committed His mother to John, and seeing the connection of John 19 with Psalm 69 and the other gospels and giving His mother to John; (Psalm 69:21 : Matt 27:48; Luke 23:36; John 19:29; Mark 15:23) makes it even stronger that he is saying Psalm 69:8 is about Jesus' brothers, the sons of Mary.
So, the virgin birth of Christ is protected, by Scripture alone; Matthew 1:18-25 and Luke chapters 1-2; but the Perpetual Virginity of Mary doctrine and dogma is un-Scriptural and not truth, therefore, it should be abandoned.
It is a man-made tradition.