Wow. I don't even know what to say, Soot.
There's at least one positive in your situation.
From your description, it sounds like your grandparents not only know how important the strength of family values are, they've always been a source of strength for you.
Ask yourself if they also instilled that strength in you.
I'm pretty sure what the answer is.
No matter what happens, you'll always have that gift they gave you.
It's not gonna be easy, but you know what?
It's your chance to be strong for them. Don't waste it.