Hi Shelly,
I'm not related (as such) to Jane Agnew, but I do have ancestral links to the Luke's, including Duncan Luke who Jane married, albeit cousins of my direct Luke ancestors.
I have managed to place most of the Lukes who originate from Lochgoilhead, Kilmorich and Strathcur in Argyll, so if you have a particular line you would like details on, I may be able to help.
FYI: Duncan & Jane Luke (ms Agnew) had at least 11 children, namely (in descending age):
William Agnew, Duncan, Lachlan MacBain, John Agnew, Peter Agnew, Margaret, Jane, Duncan (2nd), Catherine, Nicol and Helen.
Presumably the first Duncan died and named a later son Duncan too? I have yet to verify this.
In terms of other information, most of the Luke families have some connection with the fishing industry on Loch Fyne.
Many Lukes buried in Cairndow Churchyard. I will go back and check to see if it includes Duncan and Jane for you.
Hope this helps.
Andy