From my understanding, Blanche of France was betrothed to Edward II, Edward I himself and John I the Count of Holland and married Rudolf of Austria.
What if she marries Charles Robert of Hungary instead - that means she had give birth to heirs already while he is claiming Hungary and no need for a marriage alliance to Wladyslaw the Elbowhigh or Elisabeth of Poland would marry the son of Charles Robert instead, what would be its effect on history.