I wonder what would happen if you just "walked away" on a hiking trip, got declared dead, and your family family got the life insurance, but you just showed back up five years later.
You never claimed to be dead. So it seems that's not illegal. If your family really thought you were dead, they didn't do anything illegal either. Could they be forced to give the money back?
I imagine the legalities of being declared "not dead after all" would be pretty difficult.