Paula Span writing in The New York Times:

An estimated 6.6 percent of American adults aged 55 and older have no living spouse or biological children, according to a study published in 2017 in The Journals of Gerontology: Series B. (Researchers often use this definition of kinlessness because spouses and children are the relatives most apt to serve as family caregivers.)

About 1 percent fit a narrower definition — lacking a spouse or partner, children and biological siblings. The figure rises to 3 percent among women over 75.

Those aren’t high proportions, but they amount to a lot of kinless people: close to a million older Americans without a spouse or partner, children or siblings in 2019, including about 370,000 women over 75.