Opposite words for adopted:
connatural, native, inborn, inbred.
Usage samples:
  1. " It is just settled that this sweet adopted child of ours is to leave us- and at short notice too.
    "The House by the Lock", C. N. Williamson.
  2. " Not as Mrs. Joyce is rich, but The Voices have sort of adopted her.
    "Victor Ollnee's Discipline", Hamlin Garland.
  3. As Frontenac adopted the plan and sent forth the war- parties, the moral responsibility in large part rests with him.
    "The Fighting Governor A Chronicle of Frontenac", Charles W. Colby Edited by George M. Wrong and H. H. Langton.
  4. For that very reason it has been here adopted.
    "Memoir and Letters of Francis W. Newman", Giberne Sieveking.