Dad is pretty much brain dead and Step family is starving him.?

So my dad had a brain aneurysm which left him pretty much brain dead. Proceeding the initial surgery he was responding well and then had a series of strokes that left him in a vegetable state, so they say. He tries to respond when spoken to like if you tell him you love him he will mouth it back....Is this really completely brain dead? They said that these movements are involuntary but I don't buy it~My aunt held the phone to him 2 days ago when my sister called and he tried to talk to her??? My aunt put music of him singing and he made movements as if he was trying to pick the mandolin and he tapped his foot while moving his mouth!??? So the step people have had him home with hospice for almost 2 weeks now (Thursday it will be 2 weeks) with no food or fluids and he is still here!!! Isn't he being starved to death??? If he is responding that much, maybe it just isn't his time to go!!!??? Me being a biological child is there something I can do??? I have never been through anything like this if anyone knows where to start I would appreciate it.....I need to act soon! Again it has been almost 2 weeks without food or fluids and he can't hang around much longer!!! By the way we live in Michigan.