Good question. Let's start with extended family.
My uncle on my dad's side is a paranoid schizophrenic. He'd probably lose whatever marbles he's got left, poor man. The WT is his whole world.
I don't imagine that my mom's family would be any better. My grandparents would be hit really hard. I imagine my aunt would probably skip out somewhere and not come back.
And as far as immediate family is concerned, I think my sister would fare the best. She's in, but is back to her old ways of not really caring about the rules to follow them completely. She'd land on her feet, eventually. My folks would be a different track. They've got depression and other health issues, and they'd certainly need more care.
I think the WT's crumbling would leave nearly all the members of my family in complete shock. I really don't know what I could do to help them, given that most of them have invested everything in the cult.