Meijer van der Horst was a son of Karel van der Horst and Reintje Turksma. He married 23 May 1934 in Amsterdam to Rosa Ketellapper, a daughter of Abraham Ketellapper and Vrouwtje Kloot. the couple had two children.
Also Rosa's unmarried uncle lived in with the van der Horst family, Nathan Ketellapper, a brother of Rosa's father Abraham.
Meijer was born in a family with seven children, of whom thr…