Indeed, around 1165, her great-grandfather Henry IV the Blind, Count of Namur and Luxembourg, had no children from his first marriage.

But with one more attempt to have children, Henry married his second wife, Agnes of Gelderland, who bore a daughter, Ermesinde and thus had broken the promise he had made to Baldwin.

A war ensued, with the result that Baldwin would be Henry's designated heir in Namur.

Isabelle's parents wanted to make peace with Guy over a dispute of Namur.

Guy arranged a marriage between their daughter Philippa and Edward, Prince of Wales.