On March 19, 1909, he joined St. Joseph's Normal School in Pocantico Hills and received the religious habit of the Brothers of the Christian Schools on April 24, 1910, at which time he was given the religious name Antony Ferdinand.

At the age of 20, Kilbourn volunteered for missionary work and arrived in the Philippines in 1921, the youngest Brother in Manila.

He also introduced the Palmer Method of penmanship and was one of the organizers of the Boy Scouts of the Philippines, serving on its executive board with General Carlos P. Romulo, Secretary Jorge B. Vargas and General Vicente Lim.

During World War II, Kilbourn was interned by the Japanese, along with the other American Brothers and Religious.

Lucian Athanasius was forced to return to the United States to rest.