 Complete the following phrase:  He was the son of Feodor Nikitich Romanov later known as Patriarch Filaret and of Xenia later known as the great nun Martha. He was also a first cousin once removed of the last Rurikid Tsar Feodor I through his great-aunt Anastasia Romanovna, who was the mother of Feodor I, and through marriage, a great-nephew in-law with Tsar Ivan IV of Russia. His accession marked the end of the Time of Troubles. During his reign, Russia 