Topic: Void or Inexistent Contract

Scenario: Abel sued Cain for partition of the lots inherited by both parties from their deceased father. Cain, however, moved to dismiss on the ground that some years before a final and executory judgment (based on a compromise agreement) involving the same parties, same subject matter, and same causes of action had already been rendered by a court of competent jurisdiction, and that therefore the doctrine of res judicata clearly bars the present case. Abel contends that said judgment is void because the compromise agreement had been signed in their behalf by their lawyer who had not been authorized by them to enter into such agreement, and consequently, there can be no res judicata.

Question: What is the status of the compromise agreement?