Playing as Iceland, swear fealty to Petty King of Sudreyjar. Many years later, my faction leader is the King of "Skotland" (Scotland is overwhelmingly Norse), and so I have secured a decent dynasty. Then, his wife (whose father was the previous King of Skotland) ends up causing a massive civil war as princes left right and centre make their own factions. Needless to say, while I had a strong claim, I didn't have much power. Oh, and the King died in battle. So I have a shithead child Jarl of Iceland, and his sister whom I can't arrange a marriage to anyone of significance, and a newly independent Iceland with a few token islands.
"Shit."
Until that is, I accepted Skotland as a lost cause and, knowing that Norway wants what I have to become the Kingdom of Norway, I swear fealty to the King of Norway. Suddenly, I have protection. Suddenly, I have various marriage options, as well as the strongest claim to the throne of Skotland.
I now have a massive army at my back, and I'm merely biding my time while Skotland rips itself apart before I conquer the remnants. If I play my cards right, I may be able to achieve an even bigger victory than I would've had by being Jarl of Iceland and King of Skotland; I may be able to pull off becoming King of Skotland, and eventually have my descendants be the Kings of Skotland and Norway. And it all started in Iceland.