Half-British prince Rahim al-Hussaini has been named the new Aga Khan, becoming the spiritual leader of the world’s Ismaili Muslims and taking over a philanthropic empire worth $13 billion.

Prince Karim Al-Hussaini became the Aga Khan IV and 49th hereditary iman in his family's 1,300-year-old dynasty when he was a 20-year-old student at Harvard. His grandfather, the Aga Khan III ...