Pozsony County
Baron János (IV) Jeszenák was born into an old noble family in Pozsony (today: "Bratislava, Slovakia") on 22 January 1800. The family had lands in Királyfia, Pozsony County (today part of Šamorín). János' father was János III, Inspector of the Lutheran Diocese of Cisdanubia from 1814 to 1823, who donated his books to the Hungarian National Museum in 1808. János had a younger sister, Lujza, who married to Count Sámuel Teleki (1792–1857)