Ivan IV ("the Terrible/Dread") had three legitimate sons: Ivan V, Dmitrii, and Fedor (or Theodore as the English version). He killed his first son by striking him in the head with his staff, the second's death was controversial (murder vs. accidental suicide), and the third was an idiot known as "the Bell Ringer". Fedor's favorite past-time was to go around ringing the church bells. He didn't last long on the throne and was the last of the line that came from Russia's first (Varangian, btw) ruler, Rurik.

Can you tell I'm taking Russian history?

-Amé