Long story short: what if Edmund (OTL earl of Lancaster and Leicester), second son of King Henry III of England, becomes King of Sicily in 1263?
Long story long: OTL, Emperor Frederick II, who was also the King of Sicily, managed to make himself an enemy of a long list of Popes. When Frederick died in 1250, the last of these, Pope Innocent IV, began looking to replace Frederick's dynasty on the Sicilian throne. Sicily--which was right next door to Rome--was a Papal fief, and the Pope could theoretically invest it in anyone he chose. Innocent favoured Charles of Anjou for this appointment, as he was a brother of the pious and powerful King Louis IX of France. But Louis told his brother to refuse the offer, believing that it would set a bad example to depose Conrad, the rightful ruler.
Innocent then turned to Charles of Anjou's brother-in-law King Henry III of England, promising to make his younger son Edmund the next King of Sicily, so long as Henry agreed to pay an outrageously large sum of money to the papacy. Henry, in his naivety, accepted this offer in 1254 without having consulted with his barons, who detested the 'Sicilian Business.'
Still, it took until Innocent's successor, Pope Alexander IV, for the papacy to grow weary of the fact that Henry (restricted by his barons) had not yet paid the outrageous sum in full, and so he tore up Edmund's paperwork in Dec 1258. Still, Alexander couldn't come up with a viable replacement before his death in 1261. It would be up to his successor, Pope Urban IV, to bring Charles of Anjou back into the picture. Luckily for him, Louis IX had a change of heart before May 1263, and allowed his brother to accept the Pope's offer, eventually resulting in the defeat of Manfred, Conradin, and later the Sicilian Vespers and the formation of the Neapolitan Angevin dynasty.
But what if Louis IX didn't have a change of heart? What if he refused to let his brother accept the offer of the Sicilian throne a second time? Urban IV would be left in quite a bind--he needed a strong ally to oppose the Stauffers yesterday, and now he was back to square one. So, he decides to give Henry III another offer, this time without requiring him to pay such a large sum--all Henry has to do is get his butt to Sicily and Urban will invest Edmund with the kingdom.
Now for the knock-ons:
1) How do the barons take the Sicilian business 2.0? Henry wasn't deterred by their coolness before, and now the barrier to entry is a lot lower (all he has to do is get enough support to launch a campaign), but I still can't imagine they'd be too happy about the arrangement. The Second Barons' War erupted in 1264 immediately following Simon de Montfort's return to England the year prior; does the rebellion against Henry grow even stronger than OTL?
2) If Henry manages to land in Sicily with an army, does he succeed in defeating Manfred? Conradin? King Peter III of Aragon? Would military success abroad secure his position at home?
3) If Henry somehow succeeds in setting up his son in the Regno, how do the Sicilians feel about it? Will a rebellion against English rule break out a la the Sicilian Vespers OTL? Henry wasn't very popular in England, so I can't imagine he'd do very well in Sicily. How does Edward Longshanks fare in this scenario? Will he have time for campaigns in Wales and Scotland or will he be busy helping his brother Edmund keep his Sicilian throne?
4) How does Charles of Anjou's career turn out as only Count of Anjou and Provence? What happens in Hungary without the Angevins to claim the throne upon the extinction of the Árpáds? If the ship carrying all of Mary of Antioch's possessions still sinks in 1270, to whom does she sell her claim to Jerusalem in order to shore up funds?
Long story long: OTL, Emperor Frederick II, who was also the King of Sicily, managed to make himself an enemy of a long list of Popes. When Frederick died in 1250, the last of these, Pope Innocent IV, began looking to replace Frederick's dynasty on the Sicilian throne. Sicily--which was right next door to Rome--was a Papal fief, and the Pope could theoretically invest it in anyone he chose. Innocent favoured Charles of Anjou for this appointment, as he was a brother of the pious and powerful King Louis IX of France. But Louis told his brother to refuse the offer, believing that it would set a bad example to depose Conrad, the rightful ruler.
Innocent then turned to Charles of Anjou's brother-in-law King Henry III of England, promising to make his younger son Edmund the next King of Sicily, so long as Henry agreed to pay an outrageously large sum of money to the papacy. Henry, in his naivety, accepted this offer in 1254 without having consulted with his barons, who detested the 'Sicilian Business.'
Still, it took until Innocent's successor, Pope Alexander IV, for the papacy to grow weary of the fact that Henry (restricted by his barons) had not yet paid the outrageous sum in full, and so he tore up Edmund's paperwork in Dec 1258. Still, Alexander couldn't come up with a viable replacement before his death in 1261. It would be up to his successor, Pope Urban IV, to bring Charles of Anjou back into the picture. Luckily for him, Louis IX had a change of heart before May 1263, and allowed his brother to accept the Pope's offer, eventually resulting in the defeat of Manfred, Conradin, and later the Sicilian Vespers and the formation of the Neapolitan Angevin dynasty.
But what if Louis IX didn't have a change of heart? What if he refused to let his brother accept the offer of the Sicilian throne a second time? Urban IV would be left in quite a bind--he needed a strong ally to oppose the Stauffers yesterday, and now he was back to square one. So, he decides to give Henry III another offer, this time without requiring him to pay such a large sum--all Henry has to do is get his butt to Sicily and Urban will invest Edmund with the kingdom.
Now for the knock-ons:
1) How do the barons take the Sicilian business 2.0? Henry wasn't deterred by their coolness before, and now the barrier to entry is a lot lower (all he has to do is get enough support to launch a campaign), but I still can't imagine they'd be too happy about the arrangement. The Second Barons' War erupted in 1264 immediately following Simon de Montfort's return to England the year prior; does the rebellion against Henry grow even stronger than OTL?
2) If Henry manages to land in Sicily with an army, does he succeed in defeating Manfred? Conradin? King Peter III of Aragon? Would military success abroad secure his position at home?
3) If Henry somehow succeeds in setting up his son in the Regno, how do the Sicilians feel about it? Will a rebellion against English rule break out a la the Sicilian Vespers OTL? Henry wasn't very popular in England, so I can't imagine he'd do very well in Sicily. How does Edward Longshanks fare in this scenario? Will he have time for campaigns in Wales and Scotland or will he be busy helping his brother Edmund keep his Sicilian throne?
4) How does Charles of Anjou's career turn out as only Count of Anjou and Provence? What happens in Hungary without the Angevins to claim the throne upon the extinction of the Árpáds? If the ship carrying all of Mary of Antioch's possessions still sinks in 1270, to whom does she sell her claim to Jerusalem in order to shore up funds?