13 Children of Tsar Alexei I Mikhailovich Romanov (Aleksei & Aleksey) (29 Mar 1629-29 Jan 1676) Russia & 1st Wife 1st wife Maria Ilyinichna Miloslavskaya (1625-18 Aug 1669) Poland. The marriage was arranged by Boris Ivanovich Morozov (1590–1661) Russian statesman & Boyar who was related to Maria & days later married her sister Anna Ilyinichna Miloslavskaya.
Maria Ilyinichna Miloslavskaya (Russian: Мария Ильинична Милославская, 1625–1669) was the first wife of tsar Alexis of Russia and mother of the tsars Feodor III of Russia and Ivan V of Russia, and regent princess Sophia Alekseyevna.
Maria Ilinichna was a younger daughter of the noble Ilya Danilovich Miloslavsky. In 1648 tsar Alexis I of Russia reached the age required for marriage. The tsar was to choose his bride among hundreds of noble girls. The selection was managed by tsar’s tutor Boris Morozov, who arranged the tsar’s marriage to Maria, himself marrying her sister Anna. Another tsarina’s sister, Irina, married Prince Dmitry Dolgorukov.