In one important way a friend lacks what a brother possesses by definition: shared blood.
Yet in one important aspect the friend defies this elemental distinction, acting for all intents and purposes like the best of brothers: a friend is present permanently as can only be expected of the best of brothers.
The biblical collector of proverbs does not miss out on this most stubborn comfort:
A friend loves at all times,
and kinsfolk are born to share adversity.
As one tips toward the tribal end of the scale of social glues, the friend’s behavior becomes all the more remarkable.
The woman who finds herself navigating life’s most turbulent waters with family aboard is a fortunate woman, yet a true friend in the mix—even if only one—makes her richer still. A man does battle, sadly, against all manner of treachery, disappointment, and fickle allies. Yet just one friend makes adversity a passing affliction rather than the anteroom to ruin.
This permanence, this stickiness, this circumstantial ubiquity can be expected of blood ties. A friend does it because he chooses.
There is one, perhaps two or at most three comparable kinds of wealth in the whole world. That is all.