When Niels Christian Simonsen was born on 7 March 1834, in Tårs, Hjørring, Denmark, his father, Simon Jensen, was 36 and his mother, Maren Bertelsdatter, was 34. He married Dorthea Elisabeth Rosenkilde Madsdatter on 12 December 1856, in Råbjerg, Hjørring, Denmark. They were the parents of at least 6 sons and 5 daughters. He lived in Tårs, Børglum, Hjørring, Denmark in 1870 and Ugilt, Vennebjerg, Hjørring, Denmark in 1880. He died on 16 January 1888, in Hjørring, Denmark, at the age of 53, and was buried in Ugilt, Hjørring, Denmark.