A Book Review
This looks like a must-read:

The Kims' North Korea
Under the Loving Care of the Fatherly Leader: North Korea and the Kim Dynasty by Bradley K Martin

From this review, I learned that Kim Il-sung was born into a Christian "background":

At the center of this totalitarian world are Kim Il-sung and Kim Jong-il, who, along with the country's juche (self-reliance) ideology, have been likened by some observers to the Holy Trinity of Father, Son and Holy Ghost. Perhaps this is less surprising when one considers that Kim Il-sung was born into a Christian background, on April 15, 1912 (the same day the Titanic sunk, Kim's critics like to point out), barely two years into Japan's brutal 35-year occupation of the Korean peninsula (1910-45). At the time, Martin notes, Pyongyang had become something of a "Jerusalem" of the Far East, because of the large presence of Christians converted by American missionaries in earlier years. In fact, a large number of Korean nationalists fighting for independence from Imperial Japan were Christians. While Kim later played down his Christian background, aspects of the religion - albeit extreme - do seem to have had an impact on his life and style of governance.

An elderly Protestant professor whom I worked with a few years back was from Pyongyang originally and also referred to his hometown in his day as "The Jerusalem of the East."