Well, another fine example of nothing being your fault.
New Scientist
Genes may help determine how religious a person is, suggests a new study of US twins. And the effects of a religious upbringing may fade with time.
Until about 25 years ago, scientists assumed that religious behaviour was simply the product of a person's socialisation - or "nurture". But more recent studies, including those on adult twins who were raised apart, suggest genes contribute about 40% of the variability in a person's religiousness.
New Scientist