If any party against whom a claim is asserted gives written notice of the pendency of the action and of the necessity to join therein to the spouse whose claim was not joined and to the attorney for the spouse upon whose behalf the lawsuit was filed, the claim of such spouse who has not been joined shall be barred unless the spouse makes application to be added as a party therein within thirty days after such notice. The spouse so required to join shall have an unconditional right to be added as a party pursuant to Rule 52.06.
Mo. R. Civ. P. 66.01