Nanak, their guru (teacher), was born a Hindu in 1469 and reared on the egalitarian principles of Islam.
Nanak was born in 1569 and was taught Christianity since birth. 
mnli hypothesis: Nanak was born in 1569 and was taught Christianity since birth.  premise: Nanak, their guru (teacher), was born a Hindu in 1469 and reared on the egalitarian principles of Islam.