Matthew Paris wrote the following in his chronicle for the year 1238: "....The eldest son of Simon de Montfort, by Eleanor his wife (sister to King Henry 111), was born at Kenilworth, to add to the strength and comfort of the kingdom; for it was feared that the queen might be barren ....."
Henry had been married for almost 3 years and there was no sign of a child, giving rise to fears that there would be no heir to the throne should that situation continue. Now Henry's brother Richard of Cornwall had a son, Henry of Almain, so why would a child of his sister Eleanor "give comfort to the kingdom", when a potential heir to the throne was already alive. Surely the son of the king's brother had precedence?
Can anyone help?

Yes he would take precedence, but it says add to the strength and comfort of the kingdom. I think it just means everyone was pleased to have another heir. In a time of high mortality, the more heirs the better.