If you haven't sat down with your family to talk about a medical proxy-having your loved ones make decisions for you should you know longer be able to-you are not alone.  It's a conversation most families avoid. Here geriatrician Dr. Dennis McCullough, author of My Mother, Your Mother: Embracing "Slow Medicine," The Compassionate Approach for Caring for your Aging Loved Ones, offers ideas for how to start this important discussion-and what you'll want to cover.