Family and Formation
Theodore was born John, the son of Stephen, brother of Saint Sergius of Radonezh, who held an important position under Prince Andrew of Radonezh. After being widowed, Stephen entered monastic life and brought his twelve-year-old son to Saint Sergius's monastery.
Saint Sergius tonsured the boy with the name Theodore on the feast of Saint Theodore the Hair-Shirt Wearer (April 20), foreseeing his ascetical calling. At the monastery Theodore acquired the Greek language and the art of icon painting, formation that shaped his later work as both a hierarch and an iconographer.