People
In order to influence a child, one must be careful not to be that child's parent or grandparent.
— Don Marquis
Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The saying jokes that parents and grandparents are disqualified from influencing a child. Its advice is impossible to follow once the relationship exists, which sharpens the irony. The implied complaint is that family closeness can make persuasion harder, despite the authority that relationship might seem to promise.
Context reviewed