De la Broce was from a family of petty nobility in Touraine, and was a minor household official for Louis IX. After Louis' death in 1270, de la Broce quickly became a favorite of the new king. He accumulated a substantial fortune, built from Philip's largesse and from gifts from those hoping to cultivate his influence with the king.
This influence was greatly resented by many of the nobility and by associates of the Queen. In 1277 letters allegedly written by de la Broce were presented to Philip, which caused the king to have de la Broce arrested. He was finally hung six months later. No trial was held, and the evidence was apparently suppressed, so the contents of the letters are unknown.
De la Broce appears in Dante's Purgatorio, in Canto VI:
I saw the soul
cleft from its body out of spite and envy --
not, so it said, because it had been guilty --
I mean Pier de la Brosse,
and may the Lady of Brabant [the Queen of France]
while she's still in this world, watch
her ways -- or end among a sadder flock
(from Allen Mandelbaum's translation)