"For first time, unmarried households reign in US"

More than 14 million of them were headed by single women, another five million by single men, while 36.7 million belonged to a category described as "nonfamily households," a term that experts said referred primarily to gay or heterosexual couples cohabiting out of formal wedlock.

In addition, there were more than 30 million unmarried men and women living alone, who are not categorized as families, the Census Bureau reported.

By comparison, the number of traditional households with married couples at their core stood at slightly more than 55.2 million, or 49.8 percent of the total.