Well, first, the scenario you posit is a bit unusual. During the Industrial Revolution (on which I did my MA many moons ago) many of the men who made their money in trade and industry at some point sold their companies to live like landed gentry. Landed gentry status was the desirable form of wealth and social prestige. Trade and industry were a lower class activity. Thus we have Eliot's reference in The Wasteland:
He, the young man carbuncular, arrives,
A small house agent's clerk, with one bold stare,
One of the low on whom assurance sits
As a silk hat on a Bradford millionaire.
The suggestion being that the silk hat of the gentry fits ill on the head of a millionaire who made his money in industrial Bradford.
Not to say your scenario could not have happened. There were doubtless many variations and combinations, but going into trade was generally considered a step down for the gentry.
But 13, and the teenage years generally, are typically years of high moral certainty and simplistic moral thought. The idea that one's parents and their activities may be immoral comes very easily to a teenager. The scales have fallen from their eyes, as they begin their necessary separation from their parents, and they are full of the disillusionment that comes with realizing that the parents you have worshiped in childhood as infallible demigods have, in fact, feet of clay. The real parent the teenager sees seems like a betrayal of the ideal parent the child believed in, and the teenager, still believing in their own saintly virtue, is slow to forgive the betrayal.
But beyond that, it is a well established convention of literature to create children who speak with greater sophistication and perception than is typical of children of that age. The child in such works is really there to represent the voice of innocence. A novel is a lens, not a window, and you are under no obligation to create a psychologically or developmentally accurate portrait of child. (Consider Scout Finch and Holden Caulfield as two examples of literary children with a facility for expression well beyond that typical of their years.)