I was playing the Early campaign with the Hungarians on normal difficulty and and my king died of illness before an heir was old enough. I figured that it was game over but I got the message about a new king I'd never seen listed taking over. When I looked at the map the English were in control of all my provinces except for Hungary. Is this a bug?

The only thing I can figure out is that since I'd married off a princess to the Englishh a few turns before that they were somehow able to lay claim to my lands but how could that be?