Niels Steensen was born in Copenhagen on January 1, 1638 (Julian calendar) to goldsmith Steen Pedersen and his wife Anne Nielsdatter. We have no reliable knowledge regarding Niels Steensen’s mother’s family, but do know something about his father’s family: They were Lutheran ministers from the county of Scania, which now belongs to Sweden. They were well-educated, devout people. The family worshipped at the nearby Saint Nicholas Church. This is where Niels was baptized. The present Saint Nicholas church building is not the same as the one they knew.
Niels Steensen had a half-brother and two half-sisters, but none close to him in age. He was sickly as a child and spent a lot of time at home and in his father’s goldsmith workshop. In later years Niels Steensen was to credit his seriousness to having spent so much time in the company of adults.