I only have one way that I can think of. It's to close them on the idea with logic. Just as we all know history repeats itself, we know that we will see natural disasters and civil unrest amongst other things. Look at every "Republic" or "Democracy" in history, also. They "Spread the wealth", doling out as much as they can to as many as they can until there is nothing left to give. They quickly transform into a dictatorship. It's just a matter og studying history.
If you show your loved ones the facts, they will almost assuredly see the light. Certain things that sound far fetched are hard to grasp for most folks. Some things, like terrorism, or riots(In places that have seen them in recent history) are easy to convince people to prepare. Really, it's not so much convincing as it is explaining. Again, if you tell someone somehting that sounds kooky, they will likely think you're a kook. If you show someone logically that there are legitimate reasons that will show them they need to prepare for "Doomsday", then they are likely to hop on board..... YMMV