The second marriage for Otto, and at least the second for Adelheid (Browning, Charles. Americans of royal descent, 7th ed. Baltimore : Genealogical Pub. Co., 1969, pg. 177).
Adelaide (931?999), queen of Italy and empress of the Holy Roman Empire. Known in German as Adelheid, she was the daughter of Rudolf II of Burgundy. In 947 she married Lothair II, king of Italy. After his death in 950, Adelaide was imprisoned until 951, when Otto I, king of Germany and later emperor, rescued and married her.
After her marriage to Otto, she helped shape the policies of the Holy Roman Empire, especially during the reign (973?983) of her son, Emperor Otto II, and the minority (983?996) of her grandson, Emperor Otto III. Adelaide was noted for her piety. She died in Seltz, Alsace, on Dec. 16, 999, at one of the many monasteries she had established ("Adelaide (931?999)." Encyclopedia Americana. Grolier Online, 2014. Web. 9 Nov. 2014)