Yes, I heard when I was in Karachi a few weeks ago that Afghans and some in border areas of Pakistan have multiple wives and have 15-20 kids!! I didn't believe that but then someone else also said that. I don't know if some ethnic bias or not in those statements but Karachiites are very, very fed up with Afghans and with people from some regions of Pakistan; that's the impression I got.
However, in case of Afghanistan, no one wants to be blown up in bits in a conflict when they have employment options, of a 'purposeful' life. No one! It is in human nature. And thus 'the solution' in and for Afghanistan lies with social uplifting, education, women's emancipation, better economy BUT at the same time preventing the hordes from invading Pakistan.
There is no other way!