Edit: Canon'd [link]
I'm one of those who assume that Applejack's parents are dead, because of all the theories it would just make the most sense to me and would add some drama to the show. Of course I'm not keen on that theory (I'd be happy if they were alive), but so far, I like it best, so I had this idea for a comic a short while ago. I guess it pretty much explains itself.
Background by [link]
Twilight's Cutie Mark by [link]