When Kjeld Nielsen was born on 5 December 1718, in Jetsmark, Hvetbo, Hjørring, Denmark, his father, Niels Mortensen, was 22 and his mother, Mrs Niels, was 23. He married Else Svendsdatter on 2 December 1743, in Ingstrup, Hvetbo, Hjørring, Denmark. They were the parents of at least 3 sons and 1 daughter. He died in January 1763, in Ingstrup, Hvetbo, Hjørring, Denmark, at the age of 44, and was buried in Ingstrup, Hvetbo, Hjørring, Denmark.