It really just depends on the place, in China you had the infamous one child policy due to severe overpopulation, but in Sweden you get huge benefits for having more kids, the government encourages you to fuck, and then rewards you for doing so!!
I don't think there should be any set rules, but governments should offer benefits for sticking to what's ideal. For example: China now does something similar to this, if you only have 1 or 2 kids, you'll get discounts on healthcare, school or housing, but if you have more, those benefits are taken away. It's not a severe punishment like what we had in the early days of the one child policy, but it's still an effective way of controlling population growth.