When Israel Johan Østensen was born on 10 July 1870, in Nordland, Norway, his father, Østen Martinus Israelsen, was 42 and his mother, Gjertrud Kirstine Olsdatter, was 33. He married Emma Gurine Hansine Kristine Edvardsdatter on 4 August 1893, in Ankenes, Nordland, Norway. They were the parents of at least 3 daughters. He died on 2 November 1949, at the age of 79.