Ruby was the first one to use the word “twin.” It was a Sunday, and we were all home. I heard the telltale cries from Jace’s room, signaling that he’d woken from his afternoon nap. “Coming, buddy,” I called as I made my way upstairs to extract him from his crib. When I reached the doorway of the baby’s room, I became aware of a second cry, not so much an echo as a harmony. But