When Vasili II, Ivan III's father, was getting ready to attack Dmitry Shemyaka, he found an ally in the person of Boris of Tver. The two decided to seal the alliance by arranging a betrothal between the future Ivan III and Maria of Tver in 1452.[4] It appears that she died from poisoning in 1467. However, if one is to believe Joseph Volotsky, she had been suffering from "infirmity" since childhood. She gave birth to Ivan the Young in 1458.
References
^Reinventing the Russian Monarchy in the 1550s: Ivan the Terrible, the Dynasty, and the Church, Sergei Bogatyrev, The Slavonic and East European Review, Vol. 85, No. 2 (Apr., 2007), 278 note 29.
^ abAppanage and Muscovite Russia, Nikolay Andreyev, Companion to Russian Studies: Volume 1: An Introduction to Russian History, ed. Robert Auty, Dimitri Obolensky, (Cambridge University Press, 1991), 90.