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Lothair III, also known as Lothair of Supplinburg, was born around 1075 in the castle of Supplinburg, located in Saxony-Anhalt, Germany. He was a member of the noble Supplinburg family and later became the Duke of Saxony. Lothair III played a significant role in German politics during the 12th century and was elected as the Holy Roman Emperor in 1125, reigning until his death in 1137.