Eva twirled her tutu in front of the mirror. Her tutu and ballet shoes were both the exact shade of pink. "I'm the best ballerina in my dance class," she said, holding a sparkly wand and ribbons. Neva stomped around the house in her cowboy boots and carried her lasso. "I'm not afraid of anything, " she snnounced. "I love playing outside." The eight-year-old twins looked identical, only their parents could tell them apart. They loved...