I used to hear witness parents who's kids left the witnesses by disfellowshipping or just refusing to have anymore to do with the witnesses. It the young person turned completely against without being booted out, the parents would say they had lost their children to the world. They made every effort to cut off association with the kid, and would talk about how this child of their's would be destroyed. If they married and had children the JW parents viewed the now grown child as dead and about to be destroyed. In essesence they just viewed them as dead to them because they were not JW and would not live in the New System. They felt to invest themselves in their kids and their kids families was a waste of time and emotions. So they emotionally distanced themselves. Self preservation is key thought for these JW, they are trying to avoid mourning over their children, who they view as worthy of destruction. Their believe is so strong they mourn now rather than later t when this Armageddon wipes their family out. They feel they have no choice.
Only when they learn they've been fooled and that the Watchtower Society is not the speaker of truth do they stop this mind bending behavior. I've known some who had children get disfellowshipped and it caused them to leave the JW's too. To be cut off from their children was impossible for them. The others live by a less loving mentality and find it easier to just divorce themselves from their kids. Could we say the wheat (us) is separated for the less desireable chaff (them)? To cut off one kids from their love is just unimaginable to us because we are of a different sort. A more Godly sort perhaps. We have unconditionally love for our kids, and show it. Those who remain in and shun their children are hard hearted not unlike the ancient Jews who were willing to stone their own children for God.
I suppose one could look at the parents and determine just how little they loved their kids if they could turn their back on them so easily.
Balsam