Wis. Stat. § 769.204: Simultaneous proceedings.

(1) A tribunal of this state may exercise jurisdiction to establish a support order if the petition or comparable pleading is filed after a petition or comparable pleading is filed in another state or a foreign country only if all of the following apply:

(a) The petition or comparable pleading in this state is filed before the expiration of the time allowed in the other state or the foreign country for filing a responsive pleading challenging the exercise of jurisdiction by the other state or the foreign country.

(b) The contesting party timely challenges the exercise of jurisdiction in the other state or the foreign country.

(c) If relevant, this state is the home state of the child.

(2) A tribunal of this state may not exercise jurisdiction to establish a support order if the petition or comparable pleading is filed before a petition or comparable pleading is filed in another state or a foreign country if all of the following apply:

(a) The petition or comparable pleading in the other state or foreign country is filed before the expiration of the time allowed in this state for filing a responsive pleading challenging the exercise of jurisdiction by this state.

(b) The contesting party timely challenges the exercise of jurisdiction in this state.

(c) If relevant, the other state or foreign country is the home state of the child.