[1][2][3] Jacob Kærup was born on 13 September 1682 in the village of Nakskov on the island of Lolland in southern Denmark.
He was born to the merchant and local leader Peder Kærup and his wife Margrete Jacobsdatter, who was the daughter of a priest.
He was married in Copenhagen in 1712 to Helene Cathrine Brinch, the widow of the Danish priest Hans Hansen Hagerup (1682–1711).
The year after he became bishop, there was a major fire, burning two-thirds of the city of Christianssand including the church and school.
[1][2] He was described by Mich. Tyrholm as a good bishop having "the zeal of faith, thorough teaching, godly living, right-mindedness, a humble walk, and unremitting haste.