ahhhh just filling in a few gaps for my great great grandfather John McMillan has given me a hit on Ancestry for a family descended from his son John McMillan born 1859!

I have checked it out (downloaded the cert) I'm off out soon but John McMillan junior married a Mary Fitzpatrick in 1883 it was a Roman Catholic marriage it seems so my feelings on the McMillans and Duffys are correct there seems to be a lot of Irish Catholic connections.