Mehmed VI was the last Ottoman Sultan and 36th Head of House of Osman before the family was expelled from Turkey in 1924. There have been eight Heads of House since, the current being Bayezid Osman aka Prince Şehzade Bayezid Efendi. If the Ottoman Empire hadn't been dissolve, he would currently be Grand Sultan.
So what is the heir to the now extinct empire doing? He lives in New York City as a US citizen. He was born in France, but moved to the US with his family in 1941 after his mother married a US citizen. He even served in the US Army. He worked as a librarian for years before retiring, and is currently 89, going on 90.
Osman never married and has no children. That doesn't mean the empire will have no heir, though. According to genealogies of the House of Osman, there are 25 hypothetical princes now in the line of succession after Bayezid Osman, the furthest down of which was born in 2012.
