Reichshofrat
Johann Nepomuk was born on 24 March 1768 in Prague, the ninth child of Count Franz Anton von Nostitz-Rieneck (1725-1794) and Countess Marie Alžběta Krakovská z Kolowrat (1728-1815). His father was the High Burggraf of Bohemia. His father's younger brother was Friedrich Moritz von Nostitz-Rieneck, a high-ranking Austrian general who became president of the Aulic Council shortly before his death in 1796.