“How old was Dad when he got Alzheimer’s?” “Sixty-two.” “Good,” he said. “I’m sixty-three.”

We share the same genes, the same history, and many of the same habits. The outcomes, however, are not shared—and there’s no way to know which side of the line you’ll land on.

My brother-in-law has taped signs and reminders all over the house to help my sister be as independent as possible.