Could you own some forgotten burial plots?
It happens when a family buys a family plot, for perhaps 8 or 16 graves, and does not use them all up. After a century, nobody in the family is left who remembers the plots.
Contact the cemeteries where your ancestors are buried. Ask about who owns the plots where the graves are. Maybe there are vacant spots that you can sell, or donate back to the cemetery.
Some cemeteries have rules against selling grave plots.