Looking for help with dad who has dementia. Advice?

My name is Mai ,my dad and my mum had a fling while he was stationed in Texas 57 years ago. I met up with him when I was 30. He has one other daughter Kasey who lives in Hawaii. My dad has been living with my cousin for last two years while he battled cancer then again this year. He has dementia diagnosed in 2019 and needs a lot of care. My half sister has collected to take him back to hawaii to care for him as she doesn't want to use money from the sale of his house to use for his care. He's not of sound mind but can still hold a conversation sometimes. I also belive my sister has tried to change the beneficeries on my dad's policy of which we have 50% each there is no power of attorney. There is a year wait in Hawaii for a care home so she plans to let him live independently in a rental as she doesn't want him in her home.