No information about the sojourn of the two boys (Cornelis and Diedericus) in England has been traced, but it lasted six years, and they arrived back at the Cape on 2 May 1825 (CWMA 126: 27.8.1825), aged 17 and 18 respectively.
So how is it possible for Jacomina who was born 14 September 1824 to be Diedericus's son?