Is what my brother sees in his dream, and the repeated request for a visit from a saintly figure, a vision that necessitates going to visit him, or is that considered superstition, especially since we have no connection to saintly figures?

The righteous Awliya (saints/friends of God) are the pious believers. They do not claim to bring benefit or ward off harm, for that is in the hand of Allah alone. Loving them is a permissible matter, and the prophets prayed to join them. Righteous visions are glad tidings from Allah, while bad ones are from Satan, and legal rulings are not based upon them.