Are doctors always right when they say that the brain is dead?

my uncle had a stroke. hes now in an acoma its only been five days. and in these five days hes started breathing and sqeezing our hands when we talked. Today he started gargling and it sounded like he said his daughters name. could he be talking to us? the doctors say that he will be brain dead. Is it to soon to tell that? could they be wrong? Is there any treatments we can do? He has swelling to his brain.