July 24, 1817 - September 13, 1820 Adelheid married Duke Paul Frederick Augustus of Oldenburg on 24 July 1817 at Schaumburg Castle. The princess was just 17 years old when she married the 34-year-old duke. Duke Paul Frederick Augustus was the eldest son of Duke Peter of Oldenburg, heir to the Duchy of Oldenburg, and was thus second in line of succession after his father. Adelheid and Augustus had two daughters; Amalia, who was born in 1818 an later married Prince Otto of Bavaria, the elected King of Greece, and thus became Queen consort of Greece; and Frederica, who was born in 1820 and later married Maximilian Emanuel von Washington, the son of Jakob von Washington, a distant relative of the first President of the United States George Washington.