Wow, talk about a rock and a hard place. You guys sure make me feel lucky...two healthy, responsible parents (although we had a close call this year).
I have a couple of friends whose boomer parents are in the same boat. Most of them never even had the kind of long-term, big-company job which offered a pension in the first place...it's not like they can blame it on greedy CEO's stealing their pension.
Maybe you had better sit down and talk to them, make sure you understand their intentions? And drop a few hints of your own while you're at it. It's possible they have resources you don't know about.
One friend of mine solved this dilemma by purchasing a fourplex low income rental. Both of her parents (divorced) needed a place to live, so she put them up in adjacent units, and rented the other two. Kind of payback for her split-family childhood
But definitely clear the air asap...maybe the Rents need to tighten up the budget now and just don't realize it.