With regard to this question:
It appears that there is an agreement that we define "parenting" to include people that are not related (legally speaking, as in by biology or marriage) but in a parenting role. The rule of thumb /criterion is "Would the question and answers be different if we replace the 'asker' with 'parent'?" If no, we accept it.
But what about cases where the biological parenthood seems more incidentally that the defining element in the question?
While I don't dispute that no matter how old the child a parent always feels as a parent (so no "expiry date" on that), there are many cultures where there comes a paradigm shift once the child has reached a certain age and is independent. Of course this is a continuous process, not necessarily linked to milestones like legal age, graduation, moving out, marriage or them having children of their own... (For cultures where this is not the tradition or a parenting goal, other rules apply and these questions would probably be on topic, but need clear stating of cultural context.)
So should a question where three generations of adults (or almost adults in this case) have a dispute that could arise in the same or at least very similar way if the parties involved were just long-time friends be on topic? Should we use a similar rule of thumb like "Would the questions/answers be different if we replace 'parent' with 'close friend'?"
Our own help page states:
And some subjects are considered off-topic because they're not directly related to parenting, for instance:
I don't want this page to turn into a Dear Abby site, but I see questions of the following type on the horizon:
- My mother has Alzheimer's disease, what should I look for in a good nursing home? (We do accept questions from a child's perspective!)
- Why do my Grandparents always tell the same old stories and how can I convince them to stop? (That could also be the nice old lady from next doors!)