The answer is Count. Felix Yusupov's father, Felix Felixovich Yusupov, inherited the title from his father, Nikolai Borisovich Yusupov. The title of Count in Russia was a hereditary noble rank granted by the Tsar. It was the second-highest rank in the Russian Empire, after the title of Prince.
Decoding the Enigma of Felix Yusupov: A Riveting Russian Aristocratic Challenge