I have been tracing family back, and one root GGGrandfather appears out of Nova Scotia?

I have an Alexander McMillan of Beaver Dam (1849-1930), purportedly issue of a Duncan McMillan (b1813/14) and Mary (- possible Lillian Campbell?) married about 1839 in Nova Scotia, and (2nd Marriage) 1874 to Mary Campbell (!! hence some confusion?). Some evidence Duncan was born “near Locharber Lake”. Duncan apparently moved to Beaver Dam, Wisconsin around 1845. The McMillans tend to be farmers.

Wondering whether this same Duncan is issue of one of the McMillans registered in area of Antigonish – or possibly Halifax? – And which one?

Any assistance / directions / suggestions greatly appreciated.

Perry Daroesman
Canberra, Australia