How long after probate can you contest will?

Father's will is questionable and my brother and I were not named in his will. Everything was left to his girlfriend and their daughter. Tried to file to administer his estate, but couldnt afford a lawyer at the time. Probate was started in May. Girlfriend sold some of my father's estate without being named executor. Called the probate judge and she asked us for our birth certificates but nothing else was said. If we get the money, can we still fight the probate or not?