Remembering Prince Karim Al-Husseini Aga Khan IV: A Life of Leadership and Legacy. Born on December 13, 1936, Prince Karim became the 49th Imam of Isma'ilism at just 20 years old, following the death of his grandfather, Aga Khan III. As a renowned religious leader, he dedicated his life to improving the lives of millions, particularly through the Aga Khan Development Network.