I could have told you years ago when the first airing of the Dr. Phil Family was on that these problems would be ahead.  You can't solve one problem by creating new ones.  When the first programs aired, it was obvious that the parents were not in a God fearing marrage,  they were blaming each other for their own unhappiness and the mother was the controller.  The baby, now Nathan, should  have been put up for adoption as a sign that he was loved and everyone wanted the best for him.  Instead the parents are raising him and she got pregnant again , married and now is living with someone else while not divorced.  Everyone is on a crash course and blaming everyone else because they are miserable. 
My advice is to have everyone grow up.  Mom has to stop controlling everyone's life, Dad has to start taking control of his family ,Where has he been during all this turmoil?  Both girls should be drug tested and locked in a room together alone until they can stop competing for attention.   I'm tired of all the tears, You should not make anyone else responsible for your happiness.  Arin, get out of one mess before you get into another.  Dr Phil, alittle tough love is needed here.  Yes, the 2 little ones are No1, They are sufferiing because everyone else is trying to control each other.  Tell the adults to let each other alone and just love those babys and find happiness within themselves before they can tell anyone else how to live.