Say, Queen A who only speaks German wants to marry King B who only speaks Spanish. How would they get around the language barrier? Did courts of the past have a translator or did monarchs usually just marry those who spoke the same language as they did? Or were monarchs of the past usually tutored to know several different languages and so eliminated the need for a translator?
Prior to the very end of the medieval period, virtually all writing in Europe was done in Latin. This is precisely because most literate persons were educated by the Roman Catholic Church, and the Church used Latin. This made it the lingua franca of the Middle Ages. So there's really no need for translating documents from one language to another; as long as both parties are literate, a Spaniard could easily read a German's writing.