The conversation about 'the father-in-law's house' likely provides a light-hearted subplot to alleviate tension and give readers a broader understanding of the characters.
The author most likely included the conversation about "the father-in-law's house" in paragraphs 9-11 to add a light-hearted subplot to the story, which serves to relieve any rising tension. This kind of narrative device is common in storytelling to provide readers with a temporary respite from the more intense main plot, and to showcase different aspects of the characters involved. By including this interaction, the readers are given insight into the more playful or everyday aspects of the characters, which in turn may endear them to the reader or offer a more well-rounded understanding of their personalities.
The conversation about the father-in-law's house in paragraphs 9-11 is most likely included to foreshadow a time when the term's second meaning will come into play. This conversation sets up a future event or situation that is hinted at through the use of dialogue and contextual clues. By including this conversation, the author is creating suspense and anticipation for the reader.