How to get a title in FL with only the bill of sale for my Ford Explorer?

So my sister and my dad bought the truck off some lady and her husband my sister knew and the couple lost the title and doesn't know where it is. After my sis and dad bought the truck for me the husband died and then the wife went nuts which according to my sister was already nuts and she killed her mother so now the wife is in some state prison here in FL for murder and her son who is her power of attorney wants nothing to do with his mother or the truck and won't help us get the title for the truck. It's a great truck and I'm just so lost as to what I need to do to get it on the road. Any suggestions?
P.S I know it's a crazy story but it's the truth and I could just really use any advice. Do I just bring the bill of sale to the DMV and explain to them the story?

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