If it cannot be ascertained on diligent inquiry whether a person who is or may be interested in the subject matter of the action is alive or dead, what disposition the person may have made of his or her interest, or where the person resides if alive, the person and everyone claiming under him or her may be made parties by naming the person and adding "or [his or her] unknown heirs, devisees, or assignees."
Mich. Ct. R. 2.201