Feodor I was the son of
Ivan the Terrible of
Russia. Born in
1557 and regarded as feeble-minded, Feodor was not the
heir to the
throne until Ivan accidentally killed his older son in a fit of anger a few years before he himself died in
1584. Feodor became
tsar, but was largely a puppet of his brother-in-law, one of Ivan's favorites,
Boris Godunov.
During Feodor's reign, his younger brother Dmitry died mysteriously. The official story was that Dmitry had a seizure of some kind while holding a knife, and wounded himself fatally, but many suspected Gudenov of ordering him killed. (Many in Russia at the time believed that he had managed to escape, and at least two pretenders using his name would later surface in Russia.)
Feodor died in 1598, leaving no heir and ending the line of Russian rulers descended from Rurik, and Boris Godunov succeeded him.