Emperor Michael VIII married off a bastard daughter to an Il Khan
Georgia had a number of princesses marry Seljuks - Rusudan aunt of Queen Thamar was married to Sultan Sanjar and his successor.
Thamar's daughter Queen Rusudan married a Seljuk prince. Their daughter Thamar was married off to the Seljuk Sultan.
The Empire of Trebizond married off princesses to get help notably at the end of the game time frame Theodora to Uzun Hasan
John VI of Byzantium married off his daughter Theodora to the Ottoman Orhan.
The 867 scenario starts with a couple of Iberian princesses with Ummayad husbands
As far as I know, there was even more cases in Iberia, with Christian lords intermarrying with Taifas. Not to mention the numerous cases where Christian (either from "native" Christian populations, like Franks, or converts) marrying pagan lords and being the tool to bring Christianity to pagan lands, often convincing the husband to convert. Commonplace in the British Isles, Scandinavia, Eastern Europe.