Who is XXX's sister?
Aga Khan IV
Their parents divorced in 1949, in part due to Prince Aly Khan's extramarital affairs, and Prince Aly Khan shortly after married Rita Hayworth -- with whom he had a daughter, Princess Yasmin Aga Khan, the half-sister of Aga Khan IV. The Aga Khan IV also had a half-brother, Patrick Benjamin Guinness (1931--1965), from his mother's first marriage, as Joan Yarde-Buller was previously married to Loel Guinness of the banking Guinnesses.
Yasmin Aga Khan