Oh how sad. If God does not wish to heal him in this life, I pray that he will not have a long life here on earth. Who knows though, what God has planned for him and those that come in contact with him? It truly is a mystery and challenges our faith in these situations.
I know someone that had a relative that lived to be almost 100 years old, and that person was bed ridden and blind for many of their last years. At the time, nobody could see why God would keep this person alive in this miserable state.
Years later, because of the witness of this person always talking about Jesus to all who came to visit, my friend came to believe in Christ in a crisis. They remembered the faith of this person, even though they were in pain, blind and bed ridden, and it encouraged them to turn to God in their crisis.
Sorry for the long story, but I wanted to encourage me and you all that even though we don't understand why others that love God and their families must suffer, but God DOES have a plan.