Cornelis Johannes Kapp was baptised 19.3.1809 in Swellendam. His DOB correct, I have no DOD. I did not have a DOB for his spouse Elsje Rosina - where did you get this info?
Cornelis' father was Michiel Hendrik KAPP (bap. 6.10.1763) and mother Maria Isabella VAN DER JEUGD. He had 8 siblings, 4 fem, 4 male.
Issue for Cornelis X Elsje were Michiel Hendrik, b. 4.6.1834; Elsje Jacoba Rosina Salomina, b. 3.5.1836; Maria Isabella, b. 12.7.1838; Johan Abraham, b. 30.4.1841; Cornelis Johannes Jacobus, b. 14.9.1843; Ernst Philippus, b. 27.1.1846, d. 3.12.1898; Martha Jacoba, b. 6.6.1848.
I have details for one Susanna Petronella Fredrika KAPP, b. 17.4.1894, bap. 12.8.1894 in Uniondale...d.o. Petrus Cornelis KAPP and Amerentia Margaretha Christina STROEBEL but no marriage details for her and the dates do not match up but Michiel Hendrik KAPP, b. 4.6.1834, bap. 17.1.1836 in George, (s.o. Cornelis x Elsje) married a Johanna Petronella STANDER in 13.3.1860, George. They had 14 children.
I have details further back for Cornelis KAPP - some of which you will not find in South African Genealogies. Some of the farm graves in Swellendam do have KAPP's but are not yet on record as far as I know.
Oddly enough, my Great grandfather was Pieter Willem MARAIS who married Jacomina Maria Susanna Francina KAPP. There is another Marais-Kapp marriage I have on record - both connect directly into both my Kapp and Marais lines. How do you connect in with the Kapp family?
Hope this helps.