(Washington Post illustration; iStock)

After a nearly two-year relationship, I’d recently met and fallen for a cowboy. We were lying naked in bed when Elizabeth texted me. She was no longer sure about our camping trip because she was fighting with Emmy again. I wanted to stay in bed with the cowboy. I didn’t him know very well, but he made me feel adored and full of desire. I left the casita (what New Mexicans call an inhabitable detached garage) to find Elizabeth in the big house.

I put my arm around her shoulder, feeling the thin Tweety Bird shirt she’d had since college. “It’s just the same,” she said. By which she meant that they’d been arguing about their usual things: commitment; sex (when, how often and who should initiate); starting a family; emotional availability and vulnerability.

Elizabeth had been with Emmy for two and a half years. Long before that, Elizabeth and I dated for three years in college. We’d had a volatile relationship affected by my alcoholism and infidelity and her anger and codependency.

Back then, for her, a relationship equaled being together nearly all the time. If I needed to spend time alone or with friends, she felt left out and insecure. If I needed a break when we fought, she felt abandoned. We broke up for good in 2008. After a year of silence we began emailing. Over the next eight years we became close friends, which often didn’t make sense to me. How was I so amicable with someone I’d had such a messy relationship with?

In those years, she worked a lot on herself and her codependency. Her relationship with Emmy was much healthier than ours had been, but she still struggled with what to expect from a romantic partner. She wanted Emmy to look toward forever. Emmy needed a lot of time alone and found it difficult to be sure about the longevity of their relationship, which brought out Elizabeth’s anxieties and insecurities.

When I decided to spend the summer living in the casita behind Elizabeth and Emmy’s house, I worried: Would it be weird to live with Elizabeth? Would Emmy be jealous of our shared past? Would there be sexual tension between Elizabeth and me? Emmy and me? Would Elizabeth annoy me?

Soon, though, they were waking me up in the mornings with banana shakes. We did Jillian Michaels exercise videos together and shared the responsibilities of daily life: grocery shopping, meal prep, cleanup, laundry. Because we relied and depended on each other so much, we started calling ourselves platonic sister wives. (Emmy as first wife, me as second wife.)

But where does dependence end and codependency begin? About halfway through the summer, Elizabeth and Emmy began to get anxious about my impending departure. I often felt torn between them and the cowboy. When I made a decision to be with the cowboy I felt I had to explain myself and promise them more time in the upcoming days.

One day while lying around on the casita’s full bed, looking at the sunshine streaming through the French doors, the three of us talked of a shared future. We made each other’s lives easier. We got all the benefits of living with people — camaraderie and support — but we could still retreat to our separate spaces. They wanted kids someday; I didn’t. Living with them would allow me to experience children without the pressure of being a parent, and it would give them a built-in babysitter.

Plus, we made each other work better. I woke up earlier, ate healthier and watched less TV than I did when I was in my studio in Pittsburgh. For them, having me relieved some of the pressure they put on each other.

“Don’t ever leave!” they said. I had to go back to Pittsburgh to finish graduate school. But we decided that I could come back in April and live with them for a year to try it out. They’d be together romantically, and I’d be the nonsexual sister wife — free to date whomever I wanted. Historically, I’d dated more men, but I was open to women, too.

Three weeks after I left, Emmy and Elizabeth broke up. I was sorry for Elizabeth, but I felt dumped, too. What would I do once I graduated? What about our shared future? My cowboy said that I could come live with him, which felt crazy but appealing.

I wanted to be there for Elizabeth, and to see how things felt with my cowboy, so I went to Albuquerque for a week. Reality hit with the cowboy — our lives are drastically different — and things reversed for Emmy and Elizabeth. Emmy slept in the casita, and I stayed with Elizabeth in their bedroom. Yet, they were also still close. They had no plans for anyone to move out. Things felt mostly as they had been. We still relied on each other, though in different roles: Now I was first wife.

Read more:

Will I have a husband or a wife? I’m not sure.

I’m a 44-year-old nomad. In 6 years, I’ve had 18 temporary residences.

I live with my husband and our boyfriend. Here’s how we make it work.