Sicilian Winter is a story written by lamtuna. It ran in Issue 65 at http://s2b2.livejournal.com/351934.html, and is mirrored at http://www.shousetsubangbang.com/mirror/sicilian-winter/.
Many thanks to Wrennette (wrennette.tumblr.com) for the beta!
Roger of Sicily and Muhammad al-Idrisi are real historical characters and the latter really spent around 15 year at Roger's court creating a map of the world and its commentary. His text is quite something, sometimes reading very dry, sometimes bizarre (the man had an obsession for fish species), and occasionally touchingly personal. The parts in italics at the end of the present story are directly lifted from his preface through Anneliese Nef's French translation.
Beyond this there's very little known about their private lives -- actually, virtually nothing is sure about Al-Idrisi's life beyond the fact that he lived at Roger's court at some point.
Were they lovers? Who knows. I hope I wrote it plausibly enough!
(Although I'm not sure that a man who in his description of Maghreb mentions apples that are "as big as breasts" was as gay as I wrote him. I don't care. It was an artistic appreciation of breasts. And of apples.)