Both of my paternal grandparents have already passed away; the grandmother when I was seven or so, and the grandfather in 2013. We went to both of their funeral services, but I had never actually met or spoken to either of them in person. All I know about them is their names, and lovely keepsakes we still have from the grandma.
My maternal grandmother is alive (and lives with us), but I don't know anything about my grandfather on that side, or whether or not he's still alive, where he is, etc.. I've always liked my grandma despite how bothersome she can be sometimes; she's always been a lot more motherly than my actual mom, and is more tolerable than her rowdy siblings. I don't always agree with everything she says and does, but I'd be a wreck if anything bad happened to her..