When someone dies, the rearrangement of reality that follows can reach far beyond the absence of that person. It can alter the way family members relate to each other, as old dynamics collapse and new ones form. Since it’s often difficult—sometimes nearly impossible—to function practically in the days or weeks following a death, getting affairs in order ahead of time—whether our own or someone else’s—is a practical act of kindness.

When my mother died, it was not a simple transition. She had bee...