my eldest son always loses his pencils in school so my wife now puts his name in all his things. then one time, my son saw his pencil being used by his classmate, and incidentally, his best friend. so he told his classmate that it was his pencil. his classmate claimed that it was his, and my son told him that his name was on the pencil. the classmate told my son that his mother made a mistake by writing my son's name on the pencil. this happened just recently. and we have already noticed this habit of lying by this classmate since a few years back, when my son just started schooling, since my son always invite him to come over to our house. we actually tried to convince my son to stay away from him, but since they meet everyday at school, it's difficult to separate the two.

we know the parents of that classmate and i know they won't teach their child to lie or tolerate lying since they're a bit religious. so how did this classmate learn to lie? was it congenital?