Started as Duke William I of Normandy, who became king of England in 1066. His descendant Anselm, after the family's expansion into Anjou and Brittany, took advantage of a fractured empire and invaded the HRE in 1175. He reigned for nearly 60 years, created six kingdoms, and changed the inheritance laws to primogeniture. His descendants expanded into Iberia, North Africa, Poland, etc ... until Michael II invaded the Byantine Empire, gave it to his Greek wife, and had a kid named Arnold with her who would later inherit. This man's son, Michael III, was the greatest dynasty member of all ... expanding through the Middle East, Scandinavia, and finishing off most of Iberia, North Africa, and aEgypt. He contributed 62,000 to the total score in his 94 year lifespan (his dad died when he was 6 months old and he reigned for 79 or so) ... which is now about 149,000. Family went from Normans to English to Germans to Greeks (English and Germans still the largest represented); Catholicism is spread pretty far too ... all of North Africa, 60% of Anatolia, all of the Balkans, all of Iberia, even most of Arabia has been converted. Many of the 42 kings are kinsmen of Albrecht, the current ruler. He as Holy Roman and Byzantine emperor rules England, Norway, Andalucia, and Nubia directly.
Edit: And Flanders. I think Anselm owned Flanders too when he invaded the HRE. This duke of Saxony named Leopold ruled it ... really poorly. Most of the war was fought in the Low Countries ... and I think it lasted only a few years or so. Creating kingdoms is so much fun; Germany, Lotharingia, Bavaria, Burgundy, Italy, and Bohemia (which was already extant).... I was so proud. Now, kings are a dime a dozen. I got so many, I wish there was a title between kings and emperors. I've usually kept it down to one or two kingdoms per person ... and most have only one kingdom. But the king of Hungary keeps taking Africa, and the king of Germany took Bohemia long ago. My most consolidated force (quite irritating)is Aragon, Aquitaine, and (of all places) Armenia.
Edit: I should probably note that this game is not a mod; only one I play is GoT. Well, I did do the Rise of Empires one before the addition of all the empires in the latest patch(es). But I don't really need that anymore. Now, what I DO need ... is a way to take the rest of Italy....
Edit: Oh, and it's sorta 41 "kingdoms," because Scotland is one of those republics ... ruled by a "Serene Doge."