Do they happen to post about their prepping on social media? Cause if so their home address and any property in their name might have already been scraped up by scripts I and other folks (everyone has their own reason, I like to do it just for the technical challenge and entertainment value) have developed that crawl social media and other resources to identify and locate TARGETS like your parents. Seriously, I absolutely love the terribly opsec of 95% of preppers. If you publicly disclose the contents of your gunsafe online or how much food you have saved up or rounds without being associated with a serious malitia or other structured group then you are a target. Because without that group it doesn't matter how many guns or rounds of ammo you have, you can only really operate one at a time and chances are they havn't seriously trained and practice a plan for if their end times fantasy actually does turn out true so you become a target in a database. Bonus fun because most of the people I have scraped up are almost all of the type that don't want to be in any kind of database. :D