Complex sentence: Maria Ilyinichna Miloslavskaya (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.
Split into simpler sentences: Maria Ilyinichna Miloslavskaya (1625--1669) was a Russian tsaritsa as the first spouse of tsar Alexis of Russia. She was the mother of tsar Feodor III of Russia, tsar Ivan V of Russia, and the princess regent Sophia Alekseyevna.