13 Del. C. § 6-204: Simultaneous proceedings.

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

(1) 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;

(2) The contesting party timely challenges the exercise of jurisdiction in the other state or the foreign country; and

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

(b) 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:

(1) 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;

(2) The contesting party timely challenges the exercise of jurisdiction in this State; and

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