When Herzog Johann I. von Sachsen-Lauenburg was born in 1249, in Wittenberg, Seevetal, Harburg, Hanover, Prussia, Germany, his father, Herzog Albrecht von Sachsen-Wittenberg I, was 74 and his mother, Prinzessin Helene von Braunschweig-Lüneburg, was 26. He married Prinsessa von Sweden Ingeborg Birgerssdotter Folkungaätten in 1270, in Stockholm, Stockholm, Sweden. They were the parents of at least 6 sons and 5 daughters. He died on 30 July 1285, in Wittenberg, Wittenberg, Saxony-Anhalt, Germany, at the age of 36, and was buried in Wittenberg, Wittenberg, Saxony-Anhalt, Germany.