Johannes was born about 1775. Johannes' father was Diederik Koekemoer and his mother was Elizabeth Johanna Wagenaar. His paternal grandparents are <Unknown> and <Unknown>. He had two brothers named Jochem and Godlieb. He was the second oldest of the three children. He had four half-brothers and a half-sister, named Joachim, Gerrit, Diederik, Abraham and Maria.