The current birth rate is 1.8 in China, since one child is the goal but rural families, ethnic minorities and certain desirables and rich who pay the fines get to have 2 kids.
China’s birth rate was close to 6 kids from 1950s-1960s. In the 1970s, they started trying to get the birth rate down. Even in 1975, the birth rate was 2.7.
This means that the first generation of only children were born to parents with 2-5 siblings.
India is next:
Demographers expect India’s population to surpass the population of China, currently the most populous country in the world, by 2030. At that time, India is expected to have a population of more than 1.53 billion while China’s population is forecast to be at its peak of 1.46 billion (and will begin to drop in subsequent years).
India is currently home to about 1.21 billion people, representing a full 17% of the earths population. India’s 2011 census showed that the country’s population had grown by 181 million people in the prior decade.
When India gained independence from the United Kingdom sixty years ago, the country’s population was a mere 350 million. Since 1947, the population of India has more than tripled.