I'm not sure it works like that, feppe; from personal observation by dint of living in India, begging and the mutilation of babes to make them more convincingly effective props is hardly any route to a satisfactory endgame. Worse, it adds layer upon layer of responsibility onto a state that can either choose to ignore it or, should it feel obliged to act, can find itself bankrupt from the experience. I would be surprised to learn that the legions of street kids have any old relative whom they are going to help in dotage...
I didn't imply that I advocate having multiple kids in the developing world, just why they do so. Also, birth control is rare, expensive, and socially, ethically and/or religiously unacceptable in many places.