Ah  I haven't described what I mean properly. I understand what you're saying about the jaw being able to move without the mouth having to open but If I open the jaw on the skeleton or on Michael it's always the skeleton's jaw that moves and it breaks through the bottom of Michael's  jaw so to speak, it pokes through,micheals  jaw doesn't appear to move at all.  I was expecting Micheal's mouth to open, and the skeleton jaw with it if I dialed enough in but they don't move in unison at all if that makes any sense.

Got you on the IK. Thanks I'll turn it off.

Edit - Hmmm no, just tried that and even with IK off on Micheal the knees still poke through until I zero the skeleton.