Personally, I know of several cases -- and have heard of many more -- of grown children not getting along with their parents. Some of these cases that I know about have nothing to do with the JW experience.
These people -- parents and their children -- go years without speaking (although sometimes living in the same town) and actually see each other even less. Children born to the second generation are well on their way to (or INTO) adolescence before they ever see their Grampa or Gramma at the local grocery store or home improvement center.
"Who's that lady you were smiling at, Mom?" the teenager asks her/his mother.
"Oh. That's your Granny."
Here's my theory. It's a simple one. In the above situation where aged parents have no relationship with their adult children, it's the parent's fault.
As a father of a young daughter that I love more than life, I look at it like this....
I already see her as a teen, then her as a young adult, and then finally as a grown-up -- standing on her own... living her own life apart from her parents. If dialog between us (particularly her and me -- her father) is ever totally severed at any point along the way, I think it will be because I did something wrong. Either I expected too much, or or was too demanding, or didn't have enough respect for her as being her own person, or... SOMETHING.
When there is a breach in communication between a parent and their child, the parent is the reason. Period. I believe that.