There are an estimated 390,000 married same-sex couples in the United States, according to Williams Institute at the University of California, los Angeles, which tracks the demographics of gay and lesbian Americans.Another 70,000 couples living in states that do not currently permit them to wed would get married in the next three years, the institute says. Roughly 1 million same-sex couples, married and unmarried, live together in the United States, the institute says.