I am posting this to see if we can get some dialogue about it. It doesn't fit perfectly as a hypothesis for how all of the castaways are related, but it is a thought that my wife brought up. When we learned that Hurley had killed a few people with the collapse of the deck, she suggested that so far, many of the main characters that we have, have killed someone before getting to the island. There are plenty that we do not know about yet, but it does provide at least some sort of link between many of the characters (Kate, Sawyer, Jack, Hurley, Jin, AL, Sayid, Echo). Maybe as the season progresses, we will discover that some of the other characters like Charlie, Locke, etc. also had this in common. Just a thought, would love to see what you guys think of it.