why does TROY always stands up to for his brother GABRIEL

I think there are a number of reasons for this. Gabriel, or Gabe, is Troy's brother. He suffered a traumatic head injury in World War II that left a metal plate in his head. Because of his diminished mental capacity, he acts in a childlike manner and believes that he is the Angel Gabriel, waiting for St. Peter to open the gates of Heaven for all of the saved. Troy used Gabe's disability check from the army to buy the house in which the play takes place. At the time of the play, Gabe has moved into his own apartment, a fact that weighs on Troy.