The scientist's first wife, his daughter and son died of atrophy in Leningrad besieged by the Nazis. In 1916 Nikolai Kravkov married Ksenia Maximova (1892-1978), daughter of Nikolai Maximov (1861-?) Vice Governor of Perm. Nikolai Kravkov's elder brother was Vasily Kravkov (1859-1920), army medical officer of high rank, author of memories about Russo-Japanese War and World War I.  Nikolai Kravkov's younger brother was Sergey Kravkov (1873-1938), Professor of Saint Petersburg University, one of the first Russian soil scientists.