Father Gregory was born George Ivanovich Krug in St. Petersburg, Russia in 1908. While his mother was a Russian Orthodox Christian, his father was a Lutheran of Swedish origin. Thus, George was raised in the Lutheran tradition. Following the Bolshevik coup in 1917, the family moved to Estonia and at the age of nineteen George became an Orthodox Christian. He began studying art, first, in Tallin, Estonia and then in Tartu, which then was the intellectual and cultural hub of Estonia. In 1931, George moved to Paris to continue his studies at the Academy of Art. He began his career as an iconographer when he studied with Sergei Fyodorov, Dimitri Stelletsky and Julia Reitlinger (Sister Jean).
During World War II, George apparently began to suffer from depression and was hospitalized. Helped by his spiritual father, he recovered enough to leave the hospital and became a monk at the Skete of the Holy Spirit (Skit du Saint-Esprit near Mesnil-Saint-Denis, France), with the name Gregory, where he then dedicated himself to painting icons including frescoes at the skete. He also undertook fresco painting outside the skete, including the Russian Patriarchal Cathedral in Paris at which he was joined in painting by the noted iconographer Leonid Ouspensky. Father Gregory reposed in 1969.
While remaining true to the principles of the icon tradition, Fr. Gregory developed his own unique way of expressing these principles, producing icons that are stylistically unique. Among his techniques is his use of darts of white highlights that float over a sea of uneven color. He also used over-sized irises and pupils of his eyes to give an impression of tenderness, sadness devoid of sentimentality, and of a deep interior life.