AT 7 A.M., MY SISTER GAIL CAME waltzing into the kitchen in shorts and a sleeveless top—“Look at my outfit!”—even though it was a New England fall day in 2005. At 40, eight years younger than me, Gail was developmentally disabled and functioned at about the level of a six-year-old. “Let’s get you into something warmer,” I told her, and together we picked out jeans and a sweater. Gail launched into her usual morning complaint: “It’s not a good day to go to my program. I need to stay home to help you and Mom and Dad.”

“Your bus will be here in 20 minutes,” I said. Gail stormed out of the kitchen. Soon I heard the familiar slamming of doors all over the house. This habit used to drive me crazy, but now I just gritted my teeth and let her do it until she got tired of it. Sometimes I gave in and let her stay home.

After I’d gotten laid off from my