At my father’s seventy-first birthday picnic, my mother looked across the table at my eight-year-old son and said, “Next time, don’t bring the kid.” Everyone heard her, including Noah, but nobody said a word until my seventeen-year-old daughter pushed back her chair and told her grandmother, “Say that again.”

The picnic had been meant to be ordinary. Burgers were cooking on the grill, cousins were running across the yard, and adults sat around folding tables with paper plates and plastic cups of lemonade.