When my sister and I were growing up, we were almost always about the same size. We still are, actually. So we shared clothes. It was a way to double our wardrobe. But, from my point of view, I shared mine freely and she never wanted to share back. If I'd say, "I'd like to wear your blue sweater today," her answer would often be, "No, I'm wearing it." This happened so often, I eventually began to suspect that it was deliberate, her (perhaps unconscious) strategy to keep me away from her things. I'd complain to my mother and long...