Sikelgaita (also "Sichelgaita" or "Sigelgaita") (1040 - 16 April 1090) was a Lombard princess, the daughter of Guaimar IV, Prince of Salerno, and second wife of Robert Guiscard, Duke of Apulia. She married Robert in 1058, after Robert divorced his first wife Alberada, due to supposed consanguinity. Her sister Gaitelgrima had earlier married Robert's half-brother Drogo. Wikipedia
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