I think the film posits a state of almost total narcissistic alienation within that family—through the parents' sexuality, to their professional conduct, to Farrell's relationship with Keoghan's character, to the self-absorption of the children. They seem horrible to me but perhaps others are more familiar with that sort of home life?
Ultimately the extremes they reach under the influence of the Keoghan character serve, ironically, to draw them together and force them back into some form of authentic family relations, despite their horrible circumstances.
THE FAVOURITE draws on a similar structure with the tortuous perversity of the relations of power between Queen Anne, Abigail and Sarah tightening into a simulation of romantic intensity—the perversity revealed in the closing sequences to be grounded in the trauma of Anne's failed pregnancies. THE FAVOURITE is a better film though.
