Brooks uses the 1990 movie “Avalon” as a metaphor for family fracture. In the beginning, we see a large group of kinfolk at a holiday dinner:
As the years go by in the movie, the extended family plays a smaller and smaller role. By the 1960s, there’s no extended family at Thanksgiving. It’s just a young father and mother and their son and daughter, eating turkey off trays in front of the television. In the final scene, the main character is living alone in a nursing home, wondering what happened.
Thus, nuclear family is a station on the way from the tribal “tangled, loving, exhausting glory” to total loneliness.
It’s a flawed, overly dramatic setup because, while it’s the norm for today’s nuclear families to live apart from cousins and grandmas, everyone still gets invited to Thanksgiving dinners. Multigenerational gatherings are so much the cultural expectation that pundits advise starting political arguments around the holiday table: See what happens if the crazy uncle chimes in.