I don’t know how much this chart changed over time. But it kind of makes sense: people between 25-45 spend more time with children, also spend more time with partners once they retire, the age when people spend more time alone is about the same age when “children curves” turns downward. However, a comparison with the older years would be also interesting to see.
It is sad in a sense that older people spend so much time alone. I see it around.