R.M.
Hi D.,
I'm sorry I cannot help you. But I wanted to provide support. I was in the same situation. My Grandparents set a side A LOT!! of money for myself and the other grandkids when I was a teenager. That money I was relying on for a house.
A few years back, my Grandpa died, and I was presented with paperwork to sign to "Help Grandma access her money". A few years later, Grandma died & the grandkid's money, "never existed".
Family, (blood & step), can be more dishonest than strangers in some cases.
I'm sorry for what you're going through. I know the betrayal.
R.