Kinau was the eldest child of fisherman Heinrich Wilhelm Kinau and his wife, Metta Holst, on the Elbe island of Finkenwerder, near Hamburg. In 1895 he was apprenticed to his uncle, the merchant August Kinau in Geestemünde (today part of Bremerhaven), and from 1897 until 1898 he attended a commercial school in Bremerhaven. Later he was employed as an accountant in Meiningen, Bremen, Halle (Saale) and from 1907 at the shipping company Hamburg-Amerika-Linie in Hamburg. He married Rosa Elisabeth Reich in 1908, with whom he had three children.