Mo. R. Civ. P. 96.04
All persons in being who are vested, and all persons in being who might or would have become vested with an estate in said land if the event, condition, contingency or lapse of time upon which the same may be limited to vest in such person had happened or occurred at or immediately prior to the commencement of such action, shall be made parties plaintiff or defendant. The rule of representation of persons not in being by the person or person of the same class in estate or related in estate in respect to the land shall apply and all persons not in being shall be bound in such cases by such rule and as to and against all such persons both those in being and those not in being such sale shall carry full title to said lands. If an interest or estate in the land might vest in a person not in being who is not represented by a person in being of the same class or related in estate, the court shall appoint counsel to represent the interest of the person not in being.
Mo. R. Civ. P. 96.04
Committee Note-1981
This is substantially the same as prior Rule 96.03.