On account of his family relationship with the Miloslavsky family, he miscalculated the strength of the tsarevna Sophia Alekseyevna, (September 17 N.S. September 27, 1657 – regent of Russia (1682–1689) – July 3 N.S. July 14, 1704), full sister of Feodor III and third daughter, also, of Tsar Alexei I of Russia by his first wife, Maria Miloslavskaya and became one of her most energetic supporters, but contrived to join the other, and winning, side just before the final catastrophe.