This is such a broad question, there are many avenues from which to tackle it.
I'm going to propose looking at it through the lens of religion. Most world religions support the traditional family structure as well as encourage large families because it is a quick and effective way to multiply numbers. Consider the growth of Islam in Europe today. It is quickly becoming one of the most highly represented religions (even in Western Europe) not due to evangelism and conversion, but due to the simple fact that Muslims are having more children.
And this isn't a trend that is isolated to one world religion. Consider Catholics or Mormons. Here are two religions that encourage large families and consider a man blessed by the number of children he has.
Based on this, it could be probably be argued that choice of faith or religion is most highly influenced by parents. Consider how many people in the world who may not consider themselves "religious" would say, if asked what they believe and why, "Well, I guess I believe what my parents believed. It's what I knew growing up..." My guess would be a lot.