Mo. Rev. Stat. § 528.070: When name or interest of a party is unknown, what necessary.

In case one or more of such parties, or the share or quantity of interest of any of the parties be unknown to the petitioner, or be uncertain or contingent, or the ownership of the inheritance shall depend upon an executory devise, or the remainder shall be contingent, so that such parties cannot be named, the same shall be so stated in the petition.