Relationships have been clear anarchist territory since Emma Goldman and Voltairine DeCleyre explicitly rejected monogamy and marriage.
But while polyamory may be a popular alternative, it is - by definition - not simple, especially when we recognize the ways that it's coherent with exactly what is expected of us (for example, stereotypical male sexual behavior).
This pamphlet has one reprint of a three-person conversation from Anarchy: a journal of desire armed, printed many years ago, and a new conversation between three different poly people in 2012. Also included is a modified version of one of the better online polyamory FAQs.