Non-monogamous relationships seem to be on the rise. Is that surprising?

‘Monogamy isn’t on the verge of collapse – it’s still the arrangement most people prefer. But in some very measurable ways, the institutions that go with it – marriage and the nuclear family – are failing us.’ Photograph: Westend61/Getty Images

Our identical twins had been home from the hospital for just over a month when I saw a Facebook post from my friend Niko. He was also having a baby – but instead of doing it with two parents, he was doing it with three: himself (papa), his partner (mama), and her other partner (dada). In addition to having a mom and two dads, a fourth adult would also be living with the family – as the baby’s “bonus adult”.

I wasn’t surprised by this unusual arrangement; Niko has been openly non-monogamous since I met him years earlier. I was excited for him and his growing family, but I also felt a sharp mix of envy and despair.