Let those countries use contraception, make it available to all and normalize homosexuality. It's not like the ones having children are setting out to have more out of necessity as cheap labor. It's that they don't have access to cheap contraception. And making homosexuality normal allows gay people to have a normal life without children, if they so desire. No need for pretending.

More education and better access to contraceptives (or forced pop control like China which for obvious reasons, less desirable). Many of the poor just don't know how control the amount of children they produce. They are ignorant about it and often don't have easy access to birth control.