Britain's Royal Families: The Complete Genealogy, rev. ed. @ p 47, Geoffrey VII, Count of Louvain, Duke of Lower Brabant & Lower Lorraine
The cited information was published by Pimlico Random House, London, England, 1989, 1996 (Ref: p 47, Geoffrey VII, Count of Louvain, Duke of Lower Brabant & Lower Lorraine) The author/originator was Alison Weir.