Otto IV. Welf von Braunschweig was born circa 1177 in Braunschweig to Heinrich der Löwe (c1130-1195) and Matilda of England (1156-1189) and died 19 May 1218 Harzburg of unspecified causes. He married Beatrix von Staufen (1198-1212) 23 July 1212 JL . He married Maria van Brabant (1190-1260) May 1214 JL . William I of England (1027-1087), Henry II of England (1133-1189), Alfred the Great (849-899)/s, Charlemagne (747-814)/s, Hugh Capet (c940-996)/s, Rollo of Normandy (860-932)/s.