There is No such thing as overpopulation. There is only poverty.
The concept of poverty versus overpopulation needs close scrutiny. Poverty can be defined as too many people for the resources available in a geographic region. When we see humans living in poverty, we feel a certain solidarity with them. Our consciences tell us of our duty to help them out of their misery with food, shelter, infrastructure, and the means to develop their economy. [remember the beatitudes, and Christ's criteria for the last judgement, i.e., when did we see you hungry and feed you, see you naked and cloth you]
Remember that verbal engineering always precedes social engineering. By calling poverty by a new name, "overpopulation," we remove the burden for their suffering from our conscience. No longer do we feel the need to feed them. We now can say, "It's your fault. If you'd just stop making babies, you wouldn't be living in poverty. Your suffering is your own creation." So instead of corn meal, we ship them condoms. Instead of antibiotics, we send them IUDs. Instead of the blessing infrastructure would bring, we send the curse of infertility.
As I previously indicated, I do not believe that "overpopulation" per se causes poverty. In a free society with a free market, having more people generally means more brainpower and more technological progress and greater production and a steady increase in the average standard of living. Which means less overall poverty.
That being said, the consequences for a specific family of having more children might very well turn out to be poverty. It depends on the skills and circumstances of the parents. If they do not have the income to feed or care for the children they already have, and yet they continue to have more children, then they are indeed responsible for their own (and their children's) subsequent poverty. And no, that is not my fault, that is their fault. In that case their suffering is their own creation. And I certainly do not feel the need to feed them.