Is it possible for an angel from among Allah's angels to have been sent to inform me that my brother and I are among the people of Hellfire, and that my mother and my teacher are among the people of Paradise, knowing that Allah may disclose the unseen to His angels?

The fatwa (definition) confirms that the destiny of people, whether to Paradise or Hellfire, is part of the unseen (Ghayb) which only Allah knows through revelation. Therefore, it is not permissible to assert with certainty that anyone is destined for Paradise or Hellfire, except for those about whom Allah and His Messenger have testified. Whoever claims to know this has claimed knowledge of the unseen, and speaking about Allah without knowledge is forbidden. All conjectures about determining a person's destiny for Paradise or Hellfire are satanic whisperings (waswas) aimed at disheartening the servant and diverting them from repentance and righteous deeds. The duty is to turn away from these whisperings, strive in obedience to Allah, and ask Allah to make us among the people of Paradise.