I should have added more information on this.Christiana and her three children arrived in Lyttleton, NZ first aboard the Rimutaka. She travelled as “Mrs Whitfield and family”. They arrived days before Basil was registered for school. Isaiah’s son (also Isaiah) had previously emigrated to South Africa and been visiting the UK. He then returned to Natal on this sailing, ie later in 1905. He had previously arrived in England with his wife and two children but only had one child for the return trip. I’ve assumed his daughter (Dorothy N born 1896 in Cape Colonies) had died, although I can find no evidence. It crossed my mind that she may have died on the trip over from South Africa. So Isaiah Jnr, wife and son account for the three Oldburys. I believe the two Whitfields are in fact Isaiah plus Christiana’s oldest daughter Irene, her second illegitimate child. She seems to have kept out of the saga - once she arrived she took a job with a man named Reed Johnson and stayed with him in the Christchurch area for the rest of his life. I haven’t found their onward sailing from Natal to NZ although there were certainly sailings that fit. Isaiah arrived back in London from Sydney on the Osterley on 30th April 1919. He was shown as John Wilson aged 78.
