Charles Martel, son of the duke of Calabria the brother of Joanna of Naples, the son of Charles the Duke of Calabria survives infancy, Humbert of Dauphine does not sell his duchy to France in 1349 and Charles Martel marries Elisabeth, the last heir of the Kingdom of Mallorca in 1357 and because of this he inherits Montpeiller, Carlat, Provence and Mallorca in addition to the Kingdom of Naples Charles Martel and Elisabeth later has a son named Raymond, the treaty of Bretigny happens as OTL and ,Humbert of Dauphine sells his lands to to Charles Martel in 1362 instead to the King of France which causes his realm to be elevated to a duchy in the Holy Roman Empire, assisted by Emperor Charles IV he attacks Eastern Languedoc, Carlat, Lyonnais and French Provence and annexes it which causes instability in France, and later Charles Martel has another son named Louis, who was been decided to inherit Naples.
Edward the Black Prince decides to be a priest in a seminary because he decides that being a priest would make his lineage more possible to better their position in their claim to the French throne and he appointed John of Gaunt as heir and earlier he did not marry his OTL wife, John of Gaunt already had three children, Philippa, Elizabeth and Henry. Edward II of England and his Plantagenet allies take advantage of the situation caused by Charles Martel and because of the lack of French control in the western languedoc and it's isolation they defeat the Aragonese forces in the Rousillon and create a puppet duchy called the Duchy of Narbonne ruled by Aimery Lara which causes Plantagenets to gain one more ally in South of France an ally that is strong in Southern France and they have another ally in the Holy Roman Emperor.
The relations between Charles Martel and John Gaunt become good friends and they become strategic allies because of their huge lands in Southern France something that the Valois did not like.