Sorry, but no (that would've been awesome, though). He's the king of Lotharingia (still called Middle Francia), Aquitaine, Burgundy and Saxony.
They're both children of Pepin Karling, the son of Karloman, Charlie's brother. It was one of those games in which Karloman dies out of nowhere and Charlie takes all. But since succession was gavelkind, Pepin ended up inheriting the empire.
He had been matri-married to the daughter of a Croatian count of Krain, in Bavaria, who inherited the county, hence the children were raised at her court as Croatian. (You can see the little blue smudge way to the east and south of the blue blob). Later Avaria swallowed Bavaria.