When someone passes, who verifies that family has rights to cemetery plot and does funeral home need to verify and family need to provide documents?

The ownership of a cemetery plot is evidenced by a deed. Such deeds are generally not transferable except back to the cemetery. The cemetery should have records of ownership. The cemetery typically is responsible for opening the plot for burial and would do so based upon the presentation of the deed or based upon their own records. You should start by meeting with the cemetery to identify the plot owned by the deceased or family. If you can locate the cemetery deed that would settle all questions. If the cemetery deed cannot be located then the question of what happened to the deed and if it was sold back to the cemetery must be addressed.