An (un)Godly joke:
God had sex with his own mother so that he could be born.
So why does the Church disapprove of maternal incest?
God also had sex with his own grandmother, so that his mother could be born "without original sin".
This event (sex with his gran) is celebrated as the feast of the immaculate conception.
The Christian church sure likes to keep it in the family! ...... and also spread it about the congregation.