Julian Sas-Kuilovsky was born on May 1, 1826, in the village of Konyushky-Korolivsk [uk], in Sambir Raion, Lviv Oblast, Ukraine to a family of nobles.

He studied philosophy in the Lviv University which expelled him due his participation to the revolutionary risings which led to the revolution of 1848.

After a heavy wound on the face, he went to Paris where he studied in the Saint-Sulpice Seminary and on April 1, 1854, he was ordained as a priest.

On June 26, 1890, he was consecrated auxiliary bishop of the Eparchy of Przemyśl by Metropolitan Sylvester Sembratovych.

At end 1898 he was appointed Metropolitan Archbishop of Lviv, i.e. the primate of the Ukrainian Greek Catholic Church.