Have you ever throupled? That, for the unschooled, is when three individuals are in a “loving, committed relationship.” And a growing number of young Americans are doing it: a 2016 survey showed that 1 in 5 had previously been in a “consensual non-monogamous relationship,” or “CNM.” A more recent (January 2020) poll found that about one-third of U.S. adults said that their ideal relationship would be…