Quote Originally Posted by Henry the Fifth
I'm playing the Russians and my diplomats were cruising around selling maps,trade and alliances when I ran into a Portugese Princess who was willing to marry my faction heir. I didn't think Catholic Orthodox marriages where possible!
Historically, this is quite accurate. Several Catholic-Orthodox marriages took place - in fact, there was once a tentative marriage proposal from the Byzantine Empress Irene to Charlemagne, although this quickly became an engagement between her son and Charlemagne's daughter.

Quote Originally Posted by Agent Smith
Now only if you could arrange a Muslim/Christian marriage...
These were quite common - but only with Christian brides and Muslim grooms. Clearly, Christians can only have one wife, it would be unacceptable for a wife to be a Muslim and no self-respecting Muslim prince would allow his daughter/sister to convert. On the other hand, a Muslim could have several wives and, since he could be tolerant of Christians (as followers of the Book), could allow her to continue to practice her faith. The problem, of course, was that he'd never make her his chief wife, so all such marriages tended to be minor Christian nobility allying with senior Muslim royalty.

Of course, M2TW is not about duplicating history but rewriting it, so it would be nice to be able to marry into the Abbasids and then deal with impending loss of reputation amongst your Christian peers.....