When Johannes Letteboer was born on 2 July 1870, in Tubbergen, Overijssel, Netherlands, his father, Jacob Letteboer, was 35 and his mother, Aaltjen Weijteman, was 40. He married Hendrika Marsman on 6 May 1898, in Ambt Almelo, Overijssel, Netherlands. They were the parents of at least 1 daughter. In 1907, at the age of 37, his occupation is listed as opperman. He died on 2 March 1952, in Borne, Overijssel, Netherlands, at the age of 81.