When Johan Christian Berntzen was born on 20 February 1855, in Vor Frue, Copenhagen, Denmark, his father, Bernhard Berntzen, was 22 and his mother, Anne Johanne Isberg, was 27. He married Emilie Marie Johansson on 22 October 1882, in Copenhagen, Denmark. They were the parents of at least 2 sons and 2 daughters. He lived in Copenhagen, Denmark for about 15 years and Gentofte, Copenhagen, Denmark for about 5 years. He died in 1940, at the age of 85.