In Iberia from the mid-11th (Christian Era) century onward, the collapse of the Umayyad Caliphate of Cordoba into petty statelets is accompanied by the southward push of kingdoms established by the Basques, Goths, and Romans in the hills the Arabs and Berbers did not put the effort into taking.
Wait. How is this different from OTL?
Well, due to dynastic/political considerations, a few missionaries, and sheer luck the rulers of these states and a number of the inhabitants are Muslim. Heterodox sorts far more comfortable with neo-latin vernaculars than with Arabic, holding to a number of quasi-Christian/Germanic/Roman customs, and quite conscious of their distinction from the invaders from across the straits; but Muslim (and thus more reliant on local populations than adventurers from beyond the Pyrenees, although any of the latter that can be trusted to keep in order are not refused).