Frances,

Thank you very much for that - it suggests that the Hogg patriarch may well be that John Hogg.

Further offline discussion and Y- DNA analysis now gives us quite a lot of clarification:-
a) The Manxman who has been tested and matches up with a Hogg in Scotland has turned out to be descended, via an early illegitimacy, from a Manx Hogg man.
b) This tells us now that the Manx Hoggs must be directly descended from/closely related to the Hogg family who were first recorded as living in Selkirk in the early 1700s.
c) This Hogg family is only one of a number of different Hogg genetic families living in Scotland, England and Ireland
d) The Manx Hoggs therefore are related to James Hogg the Ettrick Shepherd (see Wikipedia)
e) The Y-DNA analysis also tells us that the Manx Hoggs and the Ettrick Hoggs are all descended from one Norwegian Viking man who must have come to Scotland ca 1000AD. They all show a relatively rare Y-DNA profile which matches a Norwegian man living today.
f) The Manx Hoggs therefore must have come from Scotland first, perhaps via Ireland.

An interesting story! Does anyone have a good tree for the Manx Hoggs which goes back to John Hogg?

cheers

John