I know it can be difficult to ignore the plight of suffering people - whether their suffering is self-imposed or beyond their control - but the fact of the matter is that supporting these people long-term is never going to fix anything. This is why those "One dollar will feed this child in Kenya for a whole month" commercials never tugged my heart strings. Yeah, it sucks that the kid was born into a total shithole, but by helping them and keeping them alive longer, it means there's a better chance that they'll stay alive, grow up and make more starving, HIV-positive babies that will suffer and die young, get raped or both.
In first-world countries, many broke people have shitty financial situations that are of their own making. You give a welfare Moo money long-term just for popping out brats and she has zero incentive to get off the dole. Oh sure, they might have to present proof to the welfare office that they're "trying" to find a job, but all they have to do is sabotage any interviews they get. That way, they "tried" to find a job, but they still get their ass-sitting check. If someone can't get their shit together after years and years and years of assistance, then it's because they don't want to get their shit together. I know some people take longer to do what they need to do for various reasons, but if they're allowed to be too comfortable in a crappy situation, they won't make any effort to change it. The average welfare heifer probably makes more per month than she ever would working, so why should she ever stop being on it when all she has to do is sluice ever 2-4 years to keep the money coming? Doesn't matter if the kids get what they need because they're just a means to an end.
Like Studio said, the only way to relieve some of the suffering of humans is to decrease the number of humans. And since genocide is probably still frowned upon, prevention is the best logical step. Put an ultimatum on all charity: we'll help you, but you have to quit breeding. You breed again, no more assistance. Bringing new and completely unnecessary lives into a shitty situation to suffer along with the parents just means the cycle of poverty will never be broken and innocent kids who never asked to be born will get dragged down with their retarded parents. The difference is the parents chose that shit. The kids didn't.
Even given such an ultimatum, you know there would be tons of people who "stick it to the man" and breed anyway when they don't have two nickels to rub together because people feel that breeding is a basic human right. Yeah, okay. How about the basic human rights of the children born into poverty who have a right to food, water, shelter, basic necessities and education, all of which they may not get or not get enough of because Mommy is a lazy whore who wants to milk the state for every cent she can because she "deserves" it?
If diapers are so expensive, the practical answer is don't have any fucking kids whose asses need diapers on them. Why's this such a difficult conclusion for people to reach? Taking care of an exotic pet is fucking expensive too, so I solve that problem by simply not getting a pet with expensive needs. I kinda wish we could just outlaw reproducing entirely for about five years, but I have no idea how we could legally and ethically handle the dumbshits who get knocked up anyway since forced abortions would most likely be a violation of human rights.