Quartets

Find the four groups. Each group has four personalities with something in common. There's only one solution to the puzzle.

Attempts:

US presidents
  • Franklin D. Roosevelt
  • George H. W. Bush
  • Thomas Jefferson
  • Dwight D. Eisenhower
UN secretaries-general
  • António Guterres
  • Kurt Waldheim
  • Ban Ki-moon
  • Javier Pérez de Cuéllar
Writers in Spain during the Civil War
  • Gabriel Garcia Lorca
  • ⁠George Orwell
  • John dos Passos
  • Ernest ⁠Hemingway
Nobel Peace Prize Winners
  • Henry Kissinger
  • Martin Luther King Jr.
  • Al Gore
  • Desmond Tutu