Who is Bran de Montfort from Falls the Shadow and what is their importance?

Bran de Montfort was Simon's second son and namesake. As a young man, he enjoyed drinking and carousing with his friends, sometimes to excess. While Simon is in Wales, his son is supposed to be raising an army to meet him and battle against Edward. Bran, unfortunately, decides to take a rest at his father's castle.... to party and relax. As a result, Edward attacks Bran's army, killing or running off the majority of his men. By the time Bran musters up his remaining army, he is too late to save his father at Evesham.