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