A 15 year old boy goes to confession and says "Bless me father for I have sinned"
"Confess your sins to me, my child," says the priest.
"Well you see father, every time I masturbate, and it's pretty often, I fantasise about my mother."
"Now, now,", says the priest. "What sort of disgusting, immoral, degenerate, perverted, sick sort of boy are you, to be thinking about your mother when you do that filthy thing to yourself. And with you having such a lovely younger brother!"