The Western Miroslav families stabilized after losing land to the Lombardian advance and the French Berenglings. At the same time, they carved out much of their de jure Kingdoms from the neighbouring pagans and counts, turning the mess of Karling borders into proper, Miroslav Kingdoms. The Eastern Miroslav families likewise stabilized after twice breaking the back of the emergent horde of Khazaria, the Khanates of Pannonia, with the Kingdom of Serbia driving a harsh crusade into the winters of Russia and emerging victorious in a trail of slaughtered slavs. Eventually however, the wastes became too desolate and the winters too harsh for the Serbian crusade to continue, and King Dragutin ceased expansion and began planning for succession. The succession laws of Serbia were changed from ultimogeniture to primogeniture, and Pannonia kept as ultimogeniture. Gradually every vassal outside of the Kingdom of Serbia was transferred to the 2nd son of Dragutin, and the 2nd son was personally tutored by Dragutin in virtues and in war. And here's where it gets dastardly genius.
Ever since the Byzantine Empire crumbled in the face of Abbasid, Shia Muslim, Miroslav, Lombardy and Khazari pressure (not even Jesus Christ can save you from such an onslaught) which lost them Armenia, Azerbaijan, Georgia, Cumania and much of the Crimea (needless to say, devastating losses), the Byzantine Empire was reduced to merely the Kingdom of Greece and its Mediterranean holdings. This was an issue, as was shown during the reign of the Isauros Queen and the Isauros Empress. Ultimately the Emperor of the Greek Empire was bound to the will of the Greek Monarch, yet the Greek Monarch could not exert their will effectively without the Greek Emperor's own will. More often than not this merely reduced the Byzantine Empire to a powerful, yet somehow still ineffectual state, one where the Empire was always hamstringed to the benefit of the Greek Kingdom (and more to the point - the Serbian Kingdom, and its Miroslav neighbours). The Byzantine Empire fell to such a ruinous state that eventually the Balkan Miroslavs surpassed the Byzantine Empire in strength - and that's without the Teutonic Knights also having been placed at the doorstep of the Byzantine scoundrels.
The Byzantine Empire was a strange nation to deal with. The Serbians both supported religious orders, Lombardians, pagans and muslims in their efforts to destroy the Empire, yet also wished to maintain the Empire as a strong buffer to the Shia Caliphate; one not strong enough to begin attacking the Balkan Miroslavs, as it had already been doing for centuries to mixed success. And for those who don't know what I intended to do, whether to let the Empire go extinct or not, I must tell you about the Serbia challenge if you do not already know. Serbia's borders must stay the same. Forever. Any land conquered must be land given away. Serbia must always stay independent. Under no exception is Serbia to fly the banner of any other house but Miroslav.
And here is where the cogs begin turning in the political dickings of Miroslavdom. Picture the scene here, you are Emperor Pankratios of the Byzantine Empire. You are 25 years old, born after the fall of the Byzantine Empire. You were raised with tales of the Empire's glory, of how it smashed the Abbasid dynasty, of how it once ruled everywhere from the Mediterranean to Bulgaria to Cumania. You were raised and promised by your father Maurikios that one day the Byzantine Empire would rule over its rightful lands once more. Your name itself was a callback to the ancient fighters of the Olympics who knocked each other senseless in a great display of martial prowess. Yet you fought so little, and when you did - it was hiding behind your Theodosian walls, and not from the Muslims or the Pagans or even the Lombardians. It was from Greeks. Fellow Greeks, who followed not you, but their King, King Germanos of house Symvatkes - once Greece had been Isauros, not anymore. Replaced by an upstart house that ruled more of the Empire than you. And during a great war with the Kingdom of Greece, where nearly all of Greece lays siege to Constantinople, your wife and Empress gives you a suggestion. It ashames you that she is intellectually far superior to you and the matrilineal marriage you are caught in is legal proof of this fact. Empress Ljubica sends message to her brother King Dragutin of Serbia to send help. King Dragutin shows up with 9,000 men and together you dash the rebels asunder. The victory was not won by your troops, your leadership or even your planning. But by jove, you are going to celebrate it.
A few long years pass where your wife thwarts every assassination attempt on your life whilst also bearing your children, the future rulers of the Byzantine Empire. You are acutely aware of the fact that they speak more Serb than Greek, and are stauncher Catholics. You suppose you can teach them the errors of their ways. Then all thoughts are interrupted when you hear that once more the Lombardians are invading Corsica.
You wish to send for King Dragutin's help once more, but the Serbians are still returning from their Winter campaign and no word is heard of them. Eventually King Dragutin sends a message to Empress Ljubica, who in turns sends a message to you. You are astonished, the Serbians who have fought against the Byzantine Empire for 200 years were swearing fealty! The Byzantine Empire for a day seems great, once more the Empire rules over three Kingdoms and not just one. The lands may be a bit far off the Eastern farmlands you wanted, but more land was better than none.
You then get word that King Dragutin demanded independence. You are flabbergasted, what game was the Serbian playing in this war? You unwisely rebuke King Dragutin against the advice of Empress Ljubica, who takes up arms against you. No matter, you had 4,000 troops in Corsica and the Greek King could raise 7,000 if he was willing. He wasn't. You look North to your new subject, the King of Pannonia. You are dismayed to find that the King of Pannonia is not only a Miroslav, but a Miroslav boy currently under the care of King Dragutin. The only question you have is why.
Unfortunately, you are a stupid, lusty and cruel Emperor, too short sighted to see the death of the Isauros house coming. The Isauros eastern Kingdoms fell to the Muslims, the Isauros Black Sea Kingdoms fell to the Khazari, the Isauros Bulgarian Kingdom to separatists and the Greek Kingdom to Isauros stupidity and greed. All that was left was the Throne of Constantinople; on its own, a worthless title. Yet a Byzantine Emperor, one such as Prince Nikodim Miroslav your own son, would with Pannonian and Serbian help be more than capable of crushing both the Greeks and reclaiming the lost eastern Kingdoms. The Miroslav Emperor would not be held to the whims of the Greek King.