The company assets were split during the divorce.
You or at least your brother could try filing a motion for summary judgment based on res judicata and collateral
estoppel. That should have been one of the defenses in your answer. If not, then you need to amend your answer since that is an affirmative defense. The problem is that the divorce was between him and her and for res judicata it should be between the same parties over the same issues. At least it should apply as to him. A rule that a final judgment on the merits by a court having jurisdiction is conclusive between the parties to a suit as to all matters that were litigated or that could have been litigated in that suit.
The U.S. legal system places a high value on allowing a party to litigate a civil lawsuit for money damages only once. U.S. courts employ the rule of res judicata to prevent a dissatisfied party from trying to litigate the issue a second time.
Res judicata will be applied to a pending lawsuit if several facts can be established by the party asserting the res judicata defense. First, the party must show that a final judgment on the merits of the case had been entered by a court having jurisdiction over the matter. This means that a final decision in the first lawsuit was based on the factual and legal disputes between the parties rather than a procedural defect, such as the failure to serve the defendant with legal process.
Once a court makes a final decision, it enters a final judgment in the case. The judgment recites pertinent data about the case, such as the names of the parties, the fact that a jury verdict was rendered, and the disposition made. The judgment is filed with the court administrator for that judicial jurisdiction.
The party asserting res judicata, having introduced a final judgment on the merits, must then show that the decision in the first lawsuit was conclusive as to the matters in the second suit. For example, assume that the plaintiff in the first lawsuit asserted that she was injured in an auto accident. She sues the driver of the other auto under a theory of Negligence. A jury returns a verdict that finds that the defendant was not negligent. The injured driver then files a second lawsuit alleging additional facts that would help her prove that the other driver was negligent. A court would dismiss the second lawsuit under res judicata because the second lawsuit is based on the same Cause of Action (negligence) and the same injury claim.
Under the companion rule of Collateral Estoppel, the plaintiff will not be allowed to file a second lawsuit for money damages using a different cause of action or claim. Under collateral estoppel, the parties are precluded from litigating a second lawsuit using a different cause of action based on any issue of fact common to both suits that had been litigated and determined in the first suit. For example, the plaintiff who lost her auto accident case based on a theory of negligence cannot proceed with a second lawsuit based on an allegation that the driver intentionally struck her auto, thus making it an intentional tort cause of action. A court would assert collateral estoppel because the plaintiff could have alleged an intentional tort cause of action in the original complaint.
What you will be saying is that these are issues that she could have raised in the divorce and since she did not, she is now barred from raising them.