As an answer to the other question that it is desirable to know about, namely why marriages were not arranged between the princes since there were children on both sides and it would make the alliance firmer, it is important that you should know that they were in fact discussed. But, although marriages between the children of kings may be commended, they are not easy to bring about because of the many things that have to be negotiated. Moreover, other lords, although they may have children of their own, do not openly dare to marry them outside the kingdom without permission from their liege lord, as such marriages are sometimes obstructed. Even though matters might be agreed according to the parents’ wishes, and everything is perfectly settled, Dame Fortune, powerful in all things, overturns the arrangements in unforeseen ways when she wishes to, as she did with some of those marriages that had begun to be negotiated.

Before the aforesaid peace treaty, the King of Portugal was secretly negotiating a great alliance and friendship with Prince Fernando, the [present] king's uncle and guardian, in which, among other things, they were to marry their children to each other. Once it was agreed in letters, and by people who served as intermediaries between them, this prince asked the [then] King of Castile [Enrique III] whether it pleased him that he, the prince, should negotiate the very peace treaty which we have talked about and marry his [own] children to those of the King of Portugal. The king sent word to him that, yes, he could talk about the peace treaty but that he should not get involved in marriages. So this alliance was dissolved and nothing more was done about it. This was at the time that the King of Portugal went to lay siege to Alcántara.

When afterwards Queen Catalina made it known to the King of Portugal that the prince and all the kingdom of Castile had charged her with arranging the peace treaty, he immediately wrote to her that they thus agreed that her daughter Princess Catalina should marry his son Prince Duarte, the eldest son and heir to the kingdom; through their marriage it would please God that they would avert war, and peace would come.