So Johan, if what you suggest is correct, I should start calling you Cousin!
Trouble is, how do we confirm all this? I have not found any communication on the KILGOUR, AINSLIE or AINSLEY message boards, or various surname and South African Rootsweb mailing lists which can shed any other light back to Thomas and Janet on St Helena Island, and their offspring.
If you wish I can send you the photos of the documents off-line (extract from parish register - Thomas and Janet marriage; Note about Martha Victoria on the back; Baptism of David Alexander). Together they would be about 1MB - don't want to reduce them as they are not easy to read.