My mother tells me that when my sister was born, everyone predicted that we would become best friends because we were so close in age (we're 22 months apart). However, that turned out to be not the case because our personalities were soooo different. While we get along fine now, my sister and I didn't have the best relationship growing up. If we weren't fighting, we were ignoring each other, or doing completely different activities. In fact, we didn't begin to really talk to each other — by this, I mean engaging in meaningful conversations and confiding in each other — until we were both in our mid-twenties. My mother recently observed that Claire and Aerin also seem to have completely different personalities,...