It’s enough to make any monogamist’s head spin. But the traditionalists had better get used to it.

Researchers are just beginning to study the phenomenon, but the few who do estimate that openly polyamorous families in the United States number more than half a million, with thriving contingents in nearly every major city. Over the past year, books like Open, by journalist Jenny Block; Opening Up, by sex columnist Tristan Taormino; and an updated version of The Ethical Slut—widely considered the modern “poly” Bible—have helped publicize the concept. Today there are poly blogs and podcasts, local get-togethers, and an online polyamory magazine called Loving More with 15,000 regular readers. Celebrities like actress Tilda Swinton and Carla Bruni, the first lady of France, have voiced support for nonmonogamy, while Greenan herself has become somewhat of an unofficial spokesperson, as the creator of a comic Web series about the practice—called “Family”—that’s loosely based on her life. “There have always been some loud-mouthed ironclads talking about the labors of monogamy and multiple-partner relationships,” says Ken Haslam, a retired anesthesiologist who curates a polyamory library at the Indiana University-based Kinsey Institute for Research in Sex, Gender and Reproduction. “But finally, with the Internet, the thing has really come about.”…

It’s easy to dismiss polyamory as a kind of frat-house fantasy gone wild. But in truth, the community has a decidedly feminist bent: women have been central to its creation, and “gender equality” is a publicly recognized tenet of the practice. Terisa herself is proof of that proposition, as the center of her cluster. She, Scott, and Larry have all been polyamorous since meeting in the Bay Area in the ’90s, where they were all involved with the same theater community.