Egbert II's sister, Gertrude of Brunswick, had a daughter with her second husband, Henry the Fat, Margrave of Frisia of Northeim.
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This daughter, Richenza (d. 1141) married Lothar of Süpplingenburg, who was Duke of Saxony and later became Holy Roman Emperor.
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Henry the Fat, Margrave of Northeim (d. 1101); III.