Each state has different requirements for a party to obtain sufficient periods of residency to allow a party to file for divorce. For example in Missouri a party must be a resident for 90 days or longer. The location that would have jurisdiction is the last location that could enter the divorce. In all likelihood it would appear to me that Minnesota or Texas would be the proper location for the divorce. That allows the State to have subject matter jurisdiction over the divorce action. The State can not divide real property that is located in another State. Furthermore, the State would still need to obtain personal jurisdiction over your son. This means that he would need to be served with a petition from that State and have some minimal contact with that State. If served with a divorce petition from North Dakota you would need to retain an attorney in Grand Forks and ask them to file a Motion to Dismiss for lack of jurisdiction. If you have another action pending in another State he could ask that her Petition be transferred to the appropriate State. Finally, if your son is on active duty with the military he maybe able to halt the proceedings by claiming relief under the Soliders and Sailors Relief Act.