Budivoj is already on there, but I'll add his younger brother, and a slightly different slant.
Henrik Nakonid,
Count of Lubeck 1073
Your father Guthskalco was a Christian ruler of the Wends (in game Duke of Mecklenburg), who was defeated and killed by the pagan chieftain Kruto. Your half-brother Budivoj tried to reclaim your family's honor, but was ambushed and murdered by Kruto. You and your nephew, both children, are all that is left of the House of Nakonid. You're the only Christian Pomeranian ruler in the world, with access to their Light Cavalry Gussar retinues. Even many of your own courtiers are pagans. Your county is pagan. Your neighbors are Denmark (who have a de jure claim on you from day 1), the HRE (who have a de jure claim on you as soon as the Duke of Saxony saves up the money to form the Duchy of Holstein), and your arch-enemy Kruto (who, as pagan duke of Mecklenburg, could launch a conquest CB on you as soon as he had the piety). Your only assets? A strong claim on the Duchy of Mecklenburg (good luck pressing it before someone holy wars them to oblivion), a capital with plenty of empty slots but 0-0-0 tech, and whatever you can beg, steal or borrow. Oh, and the motivation to track down Kruto and say "My name is Henrik Nakonid. You killed my father (also my brother). Prepare to die!"
Historically, Henrik was able to murder Kruto with the help of Kruto's wife, and then established a powerful Christian Wendish state. His sons, in true CK2 style, started fighting each other, and the whole thing fell apart; reverting to paganism and eventually getting hit with the Wendish Crusade. Can you do better?
Actually quite doable (especially if you start a couple years later, when Henrik is old enough to marry for an alliance), but a really fun start, which can go in any number of directions.