Yet again you demonstrate your ignorance of all things Chinese.
The majority of people in China don't want three children or even two children and many are following the world-wide trend of not even one child. The Govt. in China, as in many other countries e.g. Japan, are trying to find ways to incentivise child-bearing.
According to accepted forecasts world population will top out around 2050 however by the end of the century the population of China will fall below 1B, Japan's population will halve, as will that of Saudi Arabia, Spain and most other countries.
EDIT. Perchance just came across these :
https://www.bbc.com/news/world-asia-china-57067180
https://www.bbc.com/news/health-53409521