"Grant that in your glory..."

In today's reading the Sons of Thunder, James and John asked Jesus for a special favor. They request that Jesus "Grant that in your glory
we may sit one at your right and the other at your left."
Jesus answers:

You do not know what you are asking. Can you drink the cup that I drink or be baptized with the baptism with which I am baptized?

They assure Him that they can and He continues,

The cup that I drink, you will drink,
and with the baptism with which I am baptized, you will be baptized; but to sit at my right or at my left is not mine to give but is for those for whom it has been prepared.

Now we know what the Sons of Zebedee did not know. That Jesus would enter into his glory on Calvary, nailed to a cross. Those destined by God to be at his right and left hand, revolutionaries against the Roman government, thieves at the very least, probably much worse. One destined for Heaven, the other most likely for Hell.
But we know much more. Of the two brothers both would face the possibility of martyrdom, but only one would do so on the day of Jesus' death. James, like all of the other Apostles, even loyal Peter, would abandon Jesus on that day. Eventually he would, like all the other Apostles but one, return to see the risen Christ. And eventually he would face death and drink from the cup of which Jesus drank on Calvary. As did all his brother Apostles, but one.
John, however would stand at the foot of the cross, with the two Marys, one the Mother of God, the other the holy woman from whom Jesus cast out demons. Can anyone believe that was a safe place to stand on that day? Peter feared to be linked to Christ, so much that he denied Him three times. The others ran away, one so in a hurry that he left his tunic behind.
John stood at the cross in sight of all the Romans. Likely mere feet from the centurion who pierced Our Lord with a lance. If a sword pierced the heart of Our Lady that day what fear, and pain and sorrow must have cut into his heart?
It appears that God must have taken note, because by his willingness to take up the cup of pain from which Jesus drank, John received into his care the vessel of Christs entrance to Earth, his Blessed Mother. And John was blessed with long life, and a peaceful death. The only Apostle not called to taste the cup of martyrdom.
Was this because he was the Apostle whom Jesus loved? Or was it because he was the Apostle who loved Jesus enough to face death even before Pentecost?