The second son of Cornelius van der Kemp, Rotterdam's leading reformed clergyman, and Anna Maria van Teylingen, he attended the Latin schools of Rotterdam and Dordrecht. He subsequently enrolled at the University of Leiden in 1763 where he studied medicine, but when his elder brother Didericus was appointed as professor of church history he abandoned his studies.
Army career
He joined the dragoon guards and fathered an illegitimate child, Johanna, whom he brought up himself. In 1778 he fell in love with Christina Frank. He lived with her for a year before being reprimanded by the Prince of Orange on this irregular state of affairs. As a result, he both married Stijntje, on 29 May 1779, and quit the army.
Return to medicine
Returning to his medical studies again, this in Edinburgh, he completed his Medical Doctorate within two years. He also prepared for publication a treatise in Latin on cosmology, entitled Parmenides which was published in 1781. He returned to the Netherlands, where he practised as a doctor first in Middelburg and then near Dordrecht. On 27 June 1791, his wife and daughter Antje were drowned in a yachting accident from which he only just escaped. As a result of this incident he experienced an emotional conversion back to the reformed Christianity of his family. He served as a medical officer during the revolutionary campaigns in Flanders and then as hospital superintendent at Zwijndrecht, near Dordrecht. Whilst there in 1797 he came to hear of the formation of the London Missionary Society.
Missionary work
After making contact with the London Missionary Society he helped found the Dutch version Nederlandsche Zendinggenootschap. He was ordained in London in November 1798 and began recruiting men for the society. He sailed from London in December 1798 as one of the first three agents sent by the society to Cape, arriving in March 1799. Whilst there in 1799 he published the first work in book-form in South Africa, which was an 8-page translation, into Dutch, of the London Missionary Society's letter that he brought out to the inhabitants of the Cape. Printed by V.A. Schoonberg most likely on J.C. Ritters press. Once in South Africa, after working at Gaika's Kraal near King William's Town he journeyed beyond the eastern frontier of the colony to work among the Xhosa under Chief Ngqika. From the Xhosa he received the name Jank' hanna. War between Cape Colony and the Xhosa soon drove him back and from 1801 onwards he worked exclusively within the colony, mainly with dispossessed Hottentots. In 1803 he established a mission settlement for vagrant Hottentots at Bethelsdorp where local farmers accused him of harboring lawless elements. He countered with a list of alleged ill-treatment of the Hottentots by local farmers, but the evidence proved unsatisfactory and the farmers were acquitted. On 7 April 1806 he married Sara Janse, a freed slave 45 years his junior, and had four children with her. This situation and his attitudes caused great opposition from within the colony, and he was for a time ordered by the government to leave Bethelsdorp. Armed with a background in European and classical philology, he pioneered in the study of Xhosa and Khoikhoi languages. He was recalled to Cape Town by the Governor in 1811 and died soon afterwards
In print
, one of the most popular English-language novelists in South Africa during her lifetime wrote The Burning Man about the life of van der Kemp. The life of Johannes van der Kemp during his mission in Bethelsdorp is included in the novelPraying Mantis by André Brink.
