(A) Unless the court orders otherwise for good cause, if a circuit court action involving child support, custody, or parenting time is pending, or if the circuit court has continuing jurisdiction over such matters because of a prior action:
(1) A new action concerning support, custody or parenting time of the same child must be filed as a motion in the earlier action if the relief sought would have been available in the original cause of action. If the relief sought was not available in the original action, the new action must be filed as a new complaint.
(2) A new action for the support, custody, or parenting time of a different child of the same parents must be filed in the same county if the circuit court for that county has jurisdiction over the new action and the new case must be assigned to the same judge to whom the previous action was assigned.
(3) Whenever possible, all actions involving the custody, parenting time, and support of children of the same parents shall be administered together. Unless the court finds that good cause exists not to do so, when the court enters a final order in a new action involving a new child of those parents, the order shall consolidate the provisions for custody, parenting time, and support for both that child and any children named in previous actions over which the court has jurisdiction involving the same parents. The order must reference the other cases and state that it supersedes the custody, parenting time, and support provisions of the orders entered previously in those cases. In the new action, the court may modify custody, parenting time, and support provisions in preexisting orders involving another child or children of the same parents, provided that the modification is supported by evidence presented in the new case and both parents have had an opportunity to be heard concerning the proposed modifications.
(B) When more than one circuit court action involving support, custody, or parenting time of a child is pending, or more than one circuit court has continuing jurisdiction over those matters because of prior actions, a complaint for the support, custody, or parenting time of a different child of the same parents must be filed in whichever circuit court has jurisdiction to decide the new action. If more than one of the previously involved circuit courts would have jurisdiction to decide the new action, or if the action might be filed in more than one county within a circuit:
(1) The new action must be filed in the same county as a prior action involving the parents’ separate maintenance, divorce, or annulment.
(2) If no prior action involves separate maintenance, divorce, or annulment, the new action must be filed:
(a) in the county of the circuit court that has issued a judgment affecting the majority of the parents’ children in common, or
(b) if no circuit court for a county has issued a judgment affecting a majority of the parents’ children in common, then in the county of the circuit court that has issued the most recent judgment affecting a child of the same parents.
(C) The court may enter an order that consolidates the custody, parenting time, and support provisions of multiple orders administratively when:
(1) the cases involve different children of the same parents but all other parties are the same, or
(2) more than one action involves the same child and parents.
The order must reference the other cases and state that it supersedes the custody, parenting time, and support provisions of the orders in those cases.
(D) In a case involving a dispute regarding the custody of a minor child, the court may, on motion of a party or on its own initiative, for good cause shown, appoint a guardian ad litem to represent the child and assess the costs and reasonable fees against the parties involved in full or in part.
Mich. Ct. R. 3.204