I just finished reading “Blowback” by Brad Thor, in which the Aga Khan is a character; I never knew anything about a Shia/Shiite spiritual leader, much less that one even existed.
Shi'ites believe in a Twelfth Imam, and the Ismailis do too - but most Ismailis believe that the Aga Khan line - descended from Muhammad's family - is that Imam.
As a result, they behave and teach radically differently from the Shi'ites, even though their theology is similar on the surface.
The Aga Khan's half-sister is the daughter of Rita Hayworth and she has been married to a Greek shipping tycoon and a British attorney. She went to Bennington and apparently spends most of her time raising money for Alzheimer's in memory of her mother.