Usually their names, + Hanım (Ms) or Bey (Mr) In Turkish we don't use surnames for the polite language. My first name is Merve, so adressing me in a polite way would be "Merve Hanım". My father's name is Vedat, and he would be "Vedat Bey". After seeing them for a few times, you can call your friends' parents their names +aunt and uncle. My parents names are Vedat and Gül. So, you can call my father Vedat Amca (Uncle Vedat) and mother Gül Teyze (Aunt Gül)