That might be the long-term solution to the nation's problems. But on an individual level, it would be disastrous for an unemployed person or someone worried about losing their job to increase their financial responsibilities by having kids.
That only works because of the lack of child labor laws and the lack of an advanced economy in which education is required in order to get a well-paying job in countries where extreme poverty is commonplace.
You didn't read parent right: the child will be an adult when the parents are older. The more kids you have, the more likely at least one will be successful enough as an adult to take care of you.
Just to make it clear: Spain, and the rest of Southern Europe are developed countries with high standards of living; extreme poverty is not even a prospect now.
