That is interesting, Len. I wondered if they perhaps weren't Manx Cavendishes. On first glance at the IGI they seem to have had a few children in London. I wonder why they were in the IOM and why they don't show up in the census. At least now I can try some earlier censuses. I must pursue this more tomorrow as it might sort out some other of my mystery Cavendishes who don't seem to be connected to anyone else. A marriage certificate order might be called for.

Thanks Len for that useful info.