was an American-born Greek businessman. He was the son of the Greek shipping magnate Aristotle Onassis and his first wife Tina Livanos. He and his sister Christina Onassis were upset by his father's marriage to Jacqueline Kennedy, and he was credited with attempting to improve the relationship between his father and his brother-in-law and business rival Stavros Niarchos, who in 1971 married Alexander's mother after her divorce from Aristotle Onassis.