Thinking about this.... reminds me of my own family... I believe that bebop has some wise suggestions...

You want to be with your sister.. and she will want to be with you..

somehow convincing your father to visit... while there is hospice or a voluteer neutral person in the house... might very well work out... if you can present it to your father.. like he is "winning"...

my father was a very stuborn person... and.. sometimes... it is how I managed to make... things "work"... what "really" goes on behind the scenes.. doesn't really matter... because.. really the goal is for you and your sister to be together..

and... there is a great value... for your girls... to have time with their aunt.. and

for my son.. when something similar happen... it really taught him.. how precious life is... and how fully one must live it..

my thoughts are with you...