Yes, I have a better answer: The Blessed Virgin Mary never bore any other children than the Christ Child, and that is why only She and John were at the foot of the Cross.
Christ entrusted His Church to St. Peter. Yet Peter denied Christ three times and also was not present at the foot of the Cross.
Why did Christ entrust His Mother to St. John, but His Church to St. Peter? And where were all these so-called "siblings" at the Pentecost or the Ascension?
14These all with one mind were continually devoting themselves to prayer, along with the women, and Mary the mother of Jesus, and with His brothers. Acts 1:14 NASB
Only Mary and John were at the foot of the cross??
Therefore the soldiers did these things. But standing by the cross of Jesus were His mother, and His mother's sister, Mary the wife of Clopas, and Mary Magdalene. John 19:25 NASB
You have read the account....right?
Where were all his so-called "cousins" who would be obligated to take care of their family member (Mary)? He gave the care of Mary over to John because he was there and Jesus knew he could be trusted. It's really that simple.
Jesus is the rock on which His church is built, not Peter. Then you have James, the brother of Jesus, who became a believer and who was the head of the church in Jerusalem. There were a lot of people gathered in the house at Pentecost as well as HUNDREDS who witnessed the resurrected Christ. Do you think the Holy Spirit should have identified everyone that was there? Take it up with Him!
Christ did not entrust His church to Peter. If He did, He would not have raised up Paul and the other disciples and He would have instructed the other disciples to be in submission to Peter.
Why did Christ entrust His Mother to St. John, but His Church to St. Peter? And where were all these so-called "siblings" at the Pentecost or the Ascension?
John 7:1-5 After this Jesus went about in Galilee. He would not go about in Judea, because the Jews were seeking to kill him. Now the Jews' Feast of Booths was at hand.
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.
I already told you what I thought about why His own brothers were not with Him at the cross. Reread the post.