When my father was born, there were close to 2 billions humans on earth.
When i was born, there were close to 4 billions humans on earth.
Now there are close to 8 billions humans on earth.
Don't worry. There is an upper limit of people. More people means less space for growing food.
So someday in the future we will fail to feed all the people on earth and some will die of starvation.
The way of preventing such tragedy is some kind of birth control. But this is not an easy task. Especially in the poorer regions of the world (where the birth rate is very high). Also less younger people would have to care for more old people (since the expectation of life constantly rises).
Some regions are underpopulated. Others are overpopulated.