A lot of the people in china simply are not borned in hospital 20 ago.
Every family has at least two children from where I grown up, even the official of the village. More like the case of speeding. You are not allowed, but you can get away with it, if the police are not there or feel it is better for him to not give you a ticket.
even a lot of Chinese are surprised when I talk about this with them. So be careful about the media's report. (they report what they think it is true, but might not)