No, I really don't feel sorry for the old crow.
Having said that I have been through 15 years of a parent who steadily became more senile and I can tell you when they get to the stage that that old crone is at there is no point in being there and ruining your life because they don't even recognise who you are.
If you've never been there I can understand why you would think Carol and Mark to be heartless.
I am not a fan of theirs, but they are doing right by themselves.