General Notes

I have not yet found an English translation of the French narrative at geneastar.org, but from what little I understand of the French language, Robert de Montbray led a revolt to assasinate Guillaume Le Roux in 1095. He was imprisoned for life.  The annulment of his marriage to Mathilde de L'Aigne was obtained, a condition being that she married Neel d'Aubigny the King of d'Angleterre.  This is probably not a very accurate translation and it appears there were other conditions attached to the annulment and for the sparing of Robert's life.  He apparently died destitute in 1095.
SOURCES: "Genealogy of Roger d'Aubigny" at http://www.geneastar.org (cites: F-L Jacquier <Les Ducs de Normandie de la Dynastie Vicking tableau XXXXII>.